1. Finding out bottlenecks.
2. Disk (storage) bottlenecks.
3. CPU and memory bottlenecks.
4. Network bottlenecks.

#1: top – Process Activity Command

The top program provides a dynamic real-time view of a running system i.e. actual process activity. By default, it displays the most CPU-intensive tasks running on the server and updates the list every five seconds.

Fig.01: Linux top command

Commonly Used Hot Keys

The top command provides several useful hot keys:

=> Related: How do I Find Out Linux CPU Utilization?

#2: vmstat – System Activity, Hardware and System Information

The command vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.
# vmstat 3
Sample Outputs:

procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0      0 2540988 522188 5130400    0    0     2    32    4    2  4  1 96  0  0
 1  0      0 2540988 522188 5130400    0    0     0   720 1199  665  1  0 99  0  0
 0  0      0 2540956 522188 5130400    0    0     0     0 1151 1569  4  1 95  0  0
 0  0      0 2540956 522188 5130500    0    0     0     6 1117  439  1  0 99  0  0
 0  0      0 2540940 522188 5130512    0    0     0   536 1189  932  1  0 98  0  0
 0  0      0 2538444 522188 5130588    0    0     0     0 1187 1417  4  1 96  0  0
 0  0      0 2490060 522188 5130640    0    0     0    18 1253 1123  5  1 94  0  0

Display Memory Utilization Slabinfo

# vmstat -m

Get Information About Active / Inactive Memory Pages

# vmstat -a
=> Related: How do I find out Linux Resource utilization to detect system bottlenecks?

#3: w – Find Out Who Is Logged on And What They Are Doing

w command displays information about the users currently on the machine, and their processes.
# w username
# w vivek
Sample Outputs:

 17:58:47 up 5 days, 20:28,  2 users,  load average: 0.36, 0.26, 0.24
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    10.1.3.145       14:55    5.00s  0.04s  0.02s vim /etc/resolv.conf
root     pts/1    10.1.3.145       17:43    0.00s  0.03s  0.00s w

#4: uptime – Tell How Long The System Has Been Running

The uptime command can be used to see how long the server has been running. The current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.
# uptime
Output:

 18:02:41 up 41 days, 23:42,  1 user,  load average: 0.00, 0.00, 0.00

1 can be considered as optimal load value. The load can change from system to system. For a single CPU system 1 – 3 and SMP systems 6-10 load value might be acceptable.

#5: ps – Displays The Processes

ps command will report a snapshot of the current processes. To select all processes use the -A or -e option:
# ps -A
Sample Outputs:

  PID TTY          TIME CMD
    1 ?        00:00:02 init
    2 ?        00:00:02 migration/0
    3 ?        00:00:01 ksoftirqd/0
    4 ?        00:00:00 watchdog/0
    5 ?        00:00:00 migration/1
    6 ?        00:00:15 ksoftirqd/1
....
.....
 4881 ?        00:53:28 java
 4885 tty1     00:00:00 mingetty
 4886 tty2     00:00:00 mingetty
 4887 tty3     00:00:00 mingetty
 4888 tty4     00:00:00 mingetty
 4891 tty5     00:00:00 mingetty
 4892 tty6     00:00:00 mingetty
 4893 ttyS1    00:00:00 agetty
12853 ?        00:00:00 cifsoplockd
12854 ?        00:00:00 cifsdnotifyd
14231 ?        00:10:34 lighttpd
14232 ?        00:00:00 php-cgi
54981 pts/0    00:00:00 vim
55465 ?        00:00:00 php-cgi
55546 ?        00:00:00 bind9-snmp-stat
55704 pts/1    00:00:00 ps

ps is just like top but provides more information.

Show Long Format Output

# ps -Al
To turn on extra full mode (it will show command line arguments passed to process):
# ps -AlF

To See Threads ( LWP and NLWP)

# ps -AlFH

To See Threads After Processes

# ps -AlLm

Print All Process On The Server

# ps ax
# ps axu

Print A Process Tree

# ps -ejH
# ps axjf
# pstree

Print Security Information

# ps -eo euser,ruser,suser,fuser,f,comm,label
# ps axZ
# ps -eM

See Every Process Running As User Vivek

# ps -U vivek -u vivek u

Set Output In a User-Defined Format

# ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm
# ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm
# ps -eopid,tt,user,fname,tmout,f,wchan

Display Only The Process IDs of Lighttpd

# ps -C lighttpd -o pid=
OR
# pgrep lighttpd
OR
# pgrep -u vivek php-cgi

Display The Name of PID 55977

# ps -p 55977 -o comm=

Find Out The Top 10 Memory Consuming Process

# ps -auxf | sort -nr -k 4 | head -10

Find Out top 10 CPU Consuming Process

# ps -auxf | sort -nr -k 3 | head -10

#6: free – Memory Usage

The command free displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel.
# free
Sample Output:

            total       used       free     shared    buffers     cached
Mem:      12302896    9739664    2563232          0     523124    5154740
-/+ buffers/cache:    4061800    8241096
Swap:      1052248          0    1052248

=> Related: :

1. Linux Find Out Virtual Memory PAGESIZE
2. Linux Limit CPU Usage Per Process
3. How much RAM does my Ubuntu / Fedora Linux desktop PC have?

#7: iostat – Average CPU Load, Disk Activity

The command iostat report Central Processing Unit (CPU) statistics and input/output statistics for devices, partitions and network filesystems (NFS).
# iostat
Sample Outputs:

Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 	06/26/2009
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           3.50    0.09    0.51    0.03    0.00   95.86
Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda              22.04        31.88       512.03   16193351  260102868
sda1              0.00         0.00         0.00       2166        180
sda2             22.04        31.87       512.03   16189010  260102688
sda3              0.00         0.00         0.00       1615          0

=> Related: : Linux Track NFS Directory / Disk I/O Stats

#8: sar – Collect and Report System Activity

The sar command is used to collect, report, and save system activity information. To see network counter, enter:
# sar -n DEV | more
To display the network counters from the 24th:
# sar -n DEV -f /var/log/sa/sa24 | more
You can also display real time usage using sar:
# sar 4 5
Sample Outputs:

Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in) 		06/26/2009
06:45:12 PM       CPU     %user     %nice   %system   %iowait    %steal     %idle
06:45:16 PM       all      2.00      0.00      0.22      0.00      0.00     97.78
06:45:20 PM       all      2.07      0.00      0.38      0.03      0.00     97.52
06:45:24 PM       all      0.94      0.00      0.28      0.00      0.00     98.78
06:45:28 PM       all      1.56      0.00      0.22      0.00      0.00     98.22
06:45:32 PM       all      3.53      0.00      0.25      0.03      0.00     96.19
Average:          all      2.02      0.00      0.27      0.01      0.00     97.70

=> Related: : How to collect Linux system utilization data into a file

#9: mpstat – Multiprocessor Usage

The mpstat command displays activities for each available processor, processor 0 being the first one. mpstat -P ALL to display average CPU utilization per processor:
# mpstat -P ALL
Sample Output:

Linux 2.6.18-128.1.14.el5 (www03.nixcraft.in)	 	06/26/2009
06:48:11 PM  CPU   %user   %nice    %sys %iowait    %irq   %soft  %steal   %idle    intr/s
06:48:11 PM  all    3.50    0.09    0.34    0.03    0.01    0.17    0.00   95.86   1218.04
06:48:11 PM    0    3.44    0.08    0.31    0.02    0.00    0.12    0.00   96.04   1000.31
06:48:11 PM    1    3.10    0.08    0.32    0.09    0.02    0.11    0.00   96.28     34.93
06:48:11 PM    2    4.16    0.11    0.36    0.02    0.00    0.11    0.00   95.25      0.00
06:48:11 PM    3    3.77    0.11    0.38    0.03    0.01    0.24    0.00   95.46     44.80
06:48:11 PM    4    2.96    0.07    0.29    0.04    0.02    0.10    0.00   96.52     25.91
06:48:11 PM    5    3.26    0.08    0.28    0.03    0.01    0.10    0.00   96.23     14.98
06:48:11 PM    6    4.00    0.10    0.34    0.01    0.00    0.13    0.00   95.42      3.75
06:48:11 PM    7    3.30    0.11    0.39    0.03    0.01    0.46    0.00   95.69     76.89

=> Related: : Linux display each multiple SMP CPU processors utilization individually.

#10: pmap – Process Memory Usage

The command pmap report memory map of a process. Use this command to find out causes of memory bottlenecks.
# pmap -d PID
To display process memory information for pid # 47394, enter:
# pmap -d 47394
Sample Outputs:

47394:   /usr/bin/php-cgi
Address           Kbytes Mode  Offset           Device    Mapping
0000000000400000    2584 r-x-- 0000000000000000 008:00002 php-cgi
0000000000886000     140 rw--- 0000000000286000 008:00002 php-cgi
00000000008a9000      52 rw--- 00000000008a9000 000:00000   [ anon ]
0000000000aa8000      76 rw--- 00000000002a8000 008:00002 php-cgi
000000000f678000    1980 rw--- 000000000f678000 000:00000   [ anon ]
000000314a600000     112 r-x-- 0000000000000000 008:00002 ld-2.5.so
000000314a81b000       4 r---- 000000000001b000 008:00002 ld-2.5.so
000000314a81c000       4 rw--- 000000000001c000 008:00002 ld-2.5.so
000000314aa00000    1328 r-x-- 0000000000000000 008:00002 libc-2.5.so
000000314ab4c000    2048 ----- 000000000014c000 008:00002 libc-2.5.so
.....
......
..
00002af8d48fd000       4 rw--- 0000000000006000 008:00002 xsl.so
00002af8d490c000      40 r-x-- 0000000000000000 008:00002 libnss_files-2.5.so
00002af8d4916000    2044 ----- 000000000000a000 008:00002 libnss_files-2.5.so
00002af8d4b15000       4 r---- 0000000000009000 008:00002 libnss_files-2.5.so
00002af8d4b16000       4 rw--- 000000000000a000 008:00002 libnss_files-2.5.so
00002af8d4b17000  768000 rw-s- 0000000000000000 000:00009 zero (deleted)
00007fffc95fe000      84 rw--- 00007ffffffea000 000:00000   [ stack ]
ffffffffff600000    8192 ----- 0000000000000000 000:00000   [ anon ]
mapped: 933712K    writeable/private: 4304K    shared: 768000K

The last line is very important:

• mapped: 933712K total amount of memory mapped to files
• writeable/private: 4304K the amount of private address space
• shared: 768000K the amount of address space this process is sharing with others

=> Related: : Linux find the memory used by a program / process using pmap command

#11 and #12: netstat and ss – Network Statistics

The command netstat displays network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. ss command is used to dump socket statistics. It allows showing information similar to netstat. See the following resources about ss and netstat commands:

• ss: Display Linux TCP / UDP Network and Socket Information
• Get Detailed Information About Particular IP address Connections Using netstat Command

#13: iptraf – Real-time Network Statistics

The iptraf command is interactive colorful IP LAN monitor. It is an ncurses-based IP LAN monitor that generates various network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet load info, node stats, IP checksum errors, and others. It can provide the following info in easy to read format:

• Network traffic statistics by TCP connection
• IP traffic statistics by network interface
• Network traffic statistics by protocol
• Network traffic statistics by TCP/UDP port and by packet size
• Network traffic statistics by Layer2 address

Fig.02: General interface statistics: IP traffic statistics by network interface

Fig.03 Network traffic statistics by TCP connection

#14: tcpdump – Detailed Network Traffic Analysis

The tcpdump is simple command that dump traffic on a network. However, you need good understanding of TCP/IP protocol to utilize this tool. For.e.g to display traffic info about DNS, enter:
# tcpdump -i eth1 'udp port 53'
To display all IPv4 HTTP packets to and from port 80, i.e. print only packets that contain data, not, for example, SYN and FIN packets and ACK-only packets, enter:
# tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
To display all FTP session to 202.54.1.5, enter:
# tcpdump -i eth1 'dst 202.54.1.5 and (port 21 or 20'
To display all HTTP session to 192.168.1.5:
# tcpdump -ni eth0 'dst 192.168.1.5 and tcp and port http'
Use wireshark to view detailed information about files, enter:
# tcpdump -n -i eth1 -s 0 -w output.txt src or dst port 80

#15: strace – System Calls

Trace system calls and signals. This is useful for debugging webserver and other server problems. See how to use to trace the process and see What it is doing.

#16: /Proc file system – Various Kernel Statistics

/proc file system provides detailed information about various hardware devices and other Linux kernel information. See Linux kernel /proc documentations for further details. Common /proc examples:
# cat /proc/cpuinfo
# cat /proc/meminfo
# cat /proc/zoneinfo
# cat /proc/mounts

17#: Nagios – Server And Network Monitoring

Nagios is a popular open source computer system and network monitoring application software. You can easily monitor all your hosts, network equipment and services. It can send alert when things go wrong and again when they get better. FAN is “Fully Automated Nagios”. FAN goals are to provide a Nagios installation including most tools provided by the Nagios Community. FAN provides a CDRom image in the standard ISO format, making it easy to easilly install a Nagios server. Added to this, a wide bunch of tools are including to the distribution, in order to improve the user experience around Nagios.

18#: Cacti – Web-based Monitoring Tool

Cacti is a complete network graphing solution designed to harness the power of RRDTool’s data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices. It can provide data about network, CPU, memory, logged in users, Apache, DNS servers and much more. See how to install and configure Cacti network graphing tool under CentOS / RHEL.

#19: KDE System Guard – Real-time Systems Reporting and Graphing

KSysguard is a network enabled task and system monitor application for KDE desktop. This tool can be run over ssh session. It provides lots of features such as a client/server architecture that enables monitoring of local and remote hosts. The graphical front end uses so-called sensors to retrieve the information it displays. A sensor can return simple values or more complex information like tables. For each type of information, one or more displays are provided. Displays are organized in worksheets that can be saved and loaded independently from each other. So, KSysguard is not only a simple task manager but also a very powerful tool to control large server farms.

Fig.05 KDE System Guard {Image credit: Wikipedia}

See the KSysguard handbook for detailed usage.

#20: Gnome System Monitor – Real-time Systems Reporting and Graphing

The System Monitor application enables you to display basic system information and monitor system processes, usage of system resources, and file systems. You can also use System Monitor to modify the behavior of your system. Although not as powerful as the KDE System Guard, it provides the basic information which may be useful for new users:

• Displays various basic information about the computer’s hardware and software.
• Linux Kernel version
• GNOME version
• Hardware
• Installed memory
• Processors and speeds
• System Status
• Currently available disk space
• Processes
• Memory and swap space
• Network usage
• File Systems
• Lists all mounted filesystems along with basic information about each.

Fig.06 The Gnome System Monitor application

Bonus: Additional Tools

A few more tools:

• nmap – scan your server for open ports.
• lsof – list open files, network connections and much more.
• ntop web based tool – ntop is the best tool to see network usage in a way similar to what top command does for processes i.e. it is network traffic monitoring software. You can see network status, protocol wise distribution of traffic for UDP, TCP, DNS, HTTP and other protocols.
• Conky – Another good monitoring tool for the X Window System. It is highly configurable and is able to monitor many system variables including the status of the CPU, memory, swap space, disk storage, temperatures, processes, network interfaces, battery power, system messages, e-mail inboxes etc.
• GKrellM – It can be used to monitor the status of CPUs, main memory, hard disks, network interfaces, local and remote mailboxes, and many other things.
• vnstat – vnStat is a console-based network traffic monitor. It keeps a log of hourly, daily and monthly network traffic for the selected interface(s).
• htop – htop is an enhanced version of top, the interactive process viewer, which can display the list of processes in a tree form.
• mtr – mtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool.

Did I miss something? Please add your favorite system motoring tool in the comments.

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(Src: http://www.cyberciti.biz)

1. Overview of dmidecode

Distributed Management Task Force maintains the DMI specification and SMBIOS specification. The output of the dmidecode contains several records from the DMI (Desktop Management interface) table.

Following is the record format of the dmidecode output of the DMI table.

Record Header: Handle {record id}, DMI type {dmi type id}, {record size} bytes
Record Value: {multi line record value}

• record id: Unique identifier for every record in the DMI table.
• dmi type id: Type of the record. i.e BIOS, Memory etc.,
• record size: Size of the record in the DMI table.
• multi line record values: Multi line record value for that specific DMI type.

Sample output of dmidecode command:

# dmidecode | head -15 
# dmidecode 2.9
SMBIOS 2.3 present.
56 structures occupying 1977 bytes.
Table at 0x000FB320.

Handle 0xDA00, DMI type 218, 11 bytes
OEM-specific Type
        Header and Data:
                DA 0B 00 DA B0 00 17 03 08 28 00

Handle 0x0000, DMI type 0, 20 bytes
BIOS Information
        Vendor: Dell Computer Corporation
        Version: A07
        Release Date: 01/13/2004

Get the total number of records in the DMI table as shown below:

# dmidecode | grep ^Handle | wc -l
56

(or)

# dmidecode | grep structures
56 structures occupying 1977 bytes.

2. DMI Types

DMI Type id will give information about a particular hardware component of your system. Following command with type id 4 will get the information about CPU of the system.

# dmidecode -t 4 # dmidecode 2.9
SMBIOS 2.3 present.

Handle 0x0400, DMI type 4, 35 bytes
Processor Information
        Socket Designation: Processor 1
        Type: Central Processor
        Family: Xeon
        Manufacturer: Intel
        ID: 29 0F 00 00 FF FB EB BF
        Signature: Type 0, Family 15, Model 2, Stepping 9
        Flags:
                FPU (Floating-point unit on-chip)
                VME (Virtual mode extension)
                DE (Debugging extension)
                PSE (Page size extension)
                TSC (Time stamp counter)
                MSR (Model specific registers)

Following are the different DMI types available.

       Type   Information
       ----------------------------------------
          0   BIOS
          1   System
          2   Base Board
          3   Chassis
          4   Processor
          5   Memory Controller
          6   Memory Module
          7   Cache
          8   Port Connector
          9   System Slots
         10   On Board Devices
         11   OEM Strings
         12   System Configuration Options
         13   BIOS Language
         14   Group Associations
         15   System Event Log
         16   Physical Memory Array
         17   Memory Device
         18   32-bit Memory Error
         19   Memory Array Mapped Address
         20   Memory Device Mapped Address
         21   Built-in Pointing Device
         22   Portable Battery
         23   System Reset
         24   Hardware Security
         25   System Power Controls
         26   Voltage Probe
         27   Cooling Device
         28   Temperature Probe
         29   Electrical Current Probe
         30   Out-of-band Remote Access
         31   Boot Integrity Services
         32   System Boot
         33   64-bit Memory Error
         34   Management Device
         35   Management Device Component
         36   Management Device Threshold Data
         37   Memory Channel
         38   IPMI Device
         39   Power Supply

Instead of type_id, you can also pass the keyword to the -t option of the dmidecode command. Following are the available keywords.

       Keyword     Types
       ------------------------------
       bios        0, 13
       system      1, 12, 15, 23, 32
       baseboard   2, 10
       chassis     3
       processor   4
       memory      5, 6, 16, 17
       cache       7
       connector   8
       slot        9

For example, to get all the system baseboard related information execute the following command, which will display the type_id 2 and 10

# dmidecode -t baseboard # dmidecode 2.9
SMBIOS 2.3 present.

Handle 0x0200, DMI type 2, 9 bytes
Base Board Information
        Manufacturer: Dell Computer Corporation
        Product Name: 123456
        Version: A05
        Serial Number: ..CN123456789098.

Handle 0x0A00, DMI type 10, 14 bytes
On Board Device 1 Information
        Type: SCSI Controller
        Status: Enabled
        Description: LSI Logic 53C1030 Ultra 320 SCSI
On Board Device 2 Information
        Type: SCSI Controller
        Status: Enabled
        Description: LSI Logic 53C1030 Ultra 320 SCSI
On Board Device 3 Information
        Type: Video
        Status: Enabled
        Description: ATI Rage XL PCI Video
On Board Device 4 Information
        Type: Ethernet
        Status: Enabled
        Description: Broadcom Gigabit Ethernet 1
On Board Device 5 Information
        Type: Ethernet
        Status: Enabled
        Description: Broadcom Gigabit Ethernet 2

3. Get Physical Memory (RAM) information using dmidecode

What is the maximum RAM supported by the system? In this example, this system can support maximum 8GB of RAM.

# dmidecode -t 16 # dmidecode 2.9
SMBIOS 2.3 present.

Handle 0x1000, DMI type 16, 15 bytes
Physical Memory Array
        Location: System Board Or Motherboard
        Use: System Memory
        Error Correction Type: Multi-bit ECC
 Maximum Capacity: 8 GB         Error Information Handle: Not Provided
        Number Of Devices: 4

How much memory can I expand to? From /proc/meminfo you can find out the total current memory of your system as shown below.

# grep MemTotal /proc/meminfo
MemTotal:      1034644 kB

In this example, the system has 1GB of RAM. Is this 1 x 1GB (or) 2 x 512MB (or) 4 x 256MB? This can be figured out by passing the type id 17 to the dmidecode command as shown below. Please note in the example below, if you have to expand upto 8GB of maximum RAM, you need to remove the existing 512MB from slot 1 and 2, and use 2GB RAM on all the 4 memory slots.

# dmidecode -t 17 # dmidecode 2.9
SMBIOS 2.3 present.

Handle 0x1100, DMI type 17, 23 bytes
Memory Device
        Array Handle: 0x1000
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
 Size: 512 MB [Note: Slot1 has 512 MB RAM]
        Form Factor: DIMM
        Set: 1
        Locator: DIMM_1A
        Bank Locator: Not Specified
        Type: DDR
        Type Detail: Synchronous
        Speed: 266 MHz (3.8 ns)

Handle 0x1101, DMI type 17, 23 bytes
Memory Device
        Array Handle: 0x1000
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
 Size: 512 MB [Note: Slot2 has 512 MB RAM]
        Form Factor: DIMM
        Set: 1
        Locator: DIMM_1B
        Bank Locator: Not Specified
        Type: DDR
        Type Detail: Synchronous
        Speed: 266 MHz (3.8 ns)

Handle 0x1102, DMI type 17, 23 bytes
Memory Device
        Array Handle: 0x1000
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
 Size: No Module Installed [Note: Slot3 is empty]
        Form Factor: DIMM
        Set: 2
        Locator: DIMM_2A
        Bank Locator: Not Specified
        Type: DDR
        Type Detail: Synchronous
        Speed: 266 MHz (3.8 ns)

Handle 0x1103, DMI type 17, 23 bytes
Memory Device
        Array Handle: 0x1000

        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
 Size: No Module Installed [Note: Slot4 is empty]
        Form Factor: DIMM
        Set: 2
        Locator: DIMM_2B
        Bank Locator: Not Specified
        Type: DDR
        Type Detail: Synchronous
        Speed: 266 MHz (3.8 ns)

4. Get BIOS information using dmidecode

# dmidecode -t bios # dmidecode 2.9
SMBIOS 2.3 present.

Handle 0x0000, DMI type 0, 20 bytes
BIOS Information
        Vendor: Dell Computer Corporation
        Version: A07
        Release Date: 01/13/2004
        Address: 0xF0000
        Runtime Size: 64 kB
        ROM Size: 4096 kB
        Characteristics:
                ISA is supported
                PCI is supported
                PNP is supported
                BIOS is upgradeable
                BIOS shadowing is allowed
                ESCD support is available
                Boot from CD is supported
                Selectable boot is supported
                EDD is supported
                Japanese floppy for Toshiba 1.2 MB is supported (int 13h)
                5.25"/360 KB floppy services are supported (int 13h)
                5.25"/1.2 MB floppy services are supported (int 13h)
                3.5"/720 KB floppy services are supported (int 13h)
                8042 keyboard services are supported (int 9h)
                Serial services are supported (int 14h)
                CGA/mono video services are supported (int 10h)
                ACPI is supported
                USB legacy is supported
                LS-120 boot is supported
                BIOS boot specification is supported
                Function key-initiated network boot is supported

Handle 0x0D00, DMI type 13, 22 bytes
BIOS Language Information
        Installable Languages: 1
                en|US|iso8859-1
        Currently Installed Language: en|US|iso8859-1

5. View Manufacturer, Model and Serial number of the equipment using dmidecode

You can get information about the make, model and serial number of the equipment as shown below:

# dmidecode -t system # dmidecode 2.9
SMBIOS 2.3 present.

Handle 0x0100, DMI type 1, 25 bytes
System Information
        Manufacturer: Dell Computer Corporation
        Product Name: PowerEdge 1750
        Version: Not Specified
        Serial Number: 1234567
        UUID: 4123454C-4123-1123-8123-12345603431
        Wake-up Type: Power Switch

Handle 0x0C00, DMI type 12, 5 bytes
System Configuration Options
        Option 1: NVRAM_CLR:  Clear user settable NVRAM areas and set defaults
        Option 2: PASSWD:  Close to enable password

Handle 0x2000, DMI type 32, 11 bytes
System Boot Information
        Status: No errors detected

The Oracle DR configurations on both the primary and standby servers are identical.  Thus the alias TEST points to the primary server and STTEST points to the standby server on both environments.  Only the TNSNAMES.ORA file differs on each server defining the aliases TEST and STTEST.  For example on the primary server PRSERVER, TEST points to PRSERVER as the primary server and STSERVER as the standby; where as on the standby server STSERVER the alias TEST points to STSERVER as the primary server and PRSERVER as the standby (opposite to that on PRSERVER).

TNSNAMES.ORA File on the primary server PRSERVER:

TEST.DBSUPPORTSERVICES.CO.UK =

(DESCRIPTION =

(ADDRESS_LIST =

(ADDRESS = (PROTOCOL = TCP)(HOST = PRSERVER)(PORT = 1521))

)

(CONNECT_DATA =

(SERVER = DEDICATED)

(SERVICE_NAME = TEST)

)

)

STTEST.DBSUPPORTSERVICES.CO.UK =

(DESCRIPTION =

(ADDRESS_LIST =

(ADDRESS = (PROTOCOL = TCP)(HOST = STSERVER)(PORT = 1521))

)

(CONNECT_DATA =

(SERVER = DEDICATED)

(SERVICE_NAME = TEST)

)

)

TNSNAMES.ORA File on the standby server STSERVER:

TEST.DBSUPPORTSERVICES.CO.UK =

(DESCRIPTION =

(ADDRESS_LIST =

(ADDRESS = (PROTOCOL = TCP)(HOST = STSERVER)(PORT = 1521))

)

(CONNECT_DATA =

(SERVER = DEDICATED)

(SERVICE_NAME = TEST)

)

)

STTEST.DBSUPPORTSERVICES.CO.UK =

(DESCRIPTION =

(ADDRESS_LIST =

(ADDRESS = (PROTOCOL = TCP)(HOST = PRSERVER)(PORT = 1521))

)

(CONNECT_DATA =

(SERVER = DEDICATED)

(SERVICE_NAME = TEST)

)

)

Relevant Initialisation Parameters on both Production and DR Servers:

*.log_archive_dest_1=’LOCATION=M:\Oracle-Databases\TEST\archive’

*.log_archive_dest_2=’SERVICE=STTEST.DBSUPPORTSERVICES.CO.UK REOPEN=60′

*.log_archive_dest_state_2=’ENABLE’

*.standby_archive_dest=’P:\Oracle-Databases\TEST\archive’

*.standby_file_management=’AUTO’

*.fal_client=’TEST.DBSUPPORTSERVICES.CO.UK’

*.fal_server=’STTEST.DBSUPPORTSERVICES.CO.UK’

*.archive_lag_target=900

Configuring the environments as above will allow log replication to continue after a clean switchover so that it is easy to switch back and forth between servers.  For example PRSERVER can become a standby database while STSERVER is primary and vice Aversa.

Creating a Standby Database from the Primary via RMAN

On production server:

1. 1.       Launch RMAN to connect to the TEST database and check the current RMAN configuration:

C:\ >set ORACLE_SID=TEST

C:\ >rman target /

Recovery Manager: Release 9.2.0.6.0 – Production

Copyright (c) 1995, 2002, Oracle Corporation.  All rights reserved.

connected to target database: TEST (DBID=1949209861)

RMAN> show all;

1. 2.       Backup the current production database to create a standby database:

RMAN> backup database include current controlfile for standby plus archivelog;

1. 3.       Manually copy the backup sets from I:\Oracle_Backups on the production server to I:\Oracle_Backups on the DR Server (location of backups must match on both production and DR).

1. 4.       On the DR Server start up the TEST database in nomount mode:

C:\> set ORACLE_SID=TEST

C:\> sqlplus /nolog

SQL> connect / as sysdba

SQL> startup nomount

SQL> exit

1. 5.       Create the standby database using RMAN (This assumes the database file structures will be identical on both servers):

C:\> RMAN target ‘sys/fluffy@STTEST’ auxiliary /

RMAN> duplicate target database for standby nofilenamecheck dorecover;

1. 6.       Once the DR database is created; you will need to manually add a tempfile:

SQL> alter database open read only;

SQL> alter tablespace temp add tempfile ‘F:\Oracle-Databases\TEST\TEMP01.DBF’ size 500M;

1. 7.       Put the DR database into managed standby mode:

SQL> shutdown immediate

SQL> startup nomount

SQL> alter database mount standby database;

SQL> alter database recover managed standby database disconnect;

1. 8.       On the production database switch logs to initiate replication:

SQL> alter system switch logfile;

The configuration of Dataguard is now complete.

Invoking a DR Standby Database

Overview

There are different methods you can use to invoke a standby database depending on the typical DR scenario you are facing.

The following section describes how to perform each of the above methods of invoking a standby database:

Database Switchover

Using this method you can switch backwards and forwards between the primary and DR servers (e.g. so that the primary can become DR and DR can become primary) without having to rebuild either environment:

On Primary Server:

SQL> alter database commit to switchover to standby;

SQL> shutdown immediate

SQL> startup nomount

SQL> alter database mount standby database;

SQL> alter database recover managed standby database disconnect;

The primary server is now configured as a DR standby database.

On DR Server:

SQL> alter database recover managed standby database cancel;

SQL> alter database commit to switchover to primary;

SQL> shutdown immediate

SQL> startup

The DR server is now configured as the primary database.

To switch back you just need to repeat the above process but the other way around (e.g. convert the DR database back to a standby and the primary database back to primary).

Activating a Standby Database

If the primary database is not available the standby database can be converted into the primary database as follows:

SQL> alter database recover managed standby database cancel;

SQL> alter database activate standby database;

SQL> shutdown immediate

SQL> startup

The original primary database is now obsolete and can be rebuilt as a standby database once it is available again.

Opening the Standby Database in Read Only Mode

The standby database can be opened in read only mode for querying and then converted back into a standby database without affecting the primary.

On standby server:

SQL> alter database recover managed standby database cancel;

SQL> alter database open read only;

The standby database is now open and available for querying in read only mode.

To put the standby database back into standby mode:

SQL> shutdown immediate

SQL> startup nomount

SQL> alter database mount standby database;

SQL> alter database recover managed standby database disconnect;

How to check whether the Standby Database is in Sync

On the primary server:

SQL> SELECT max(sequence#) AS “PRIMARY” FROM v$log_history;

On the standby server:

SQL> SELECT max(sequence#) AS “STANDBY”, applied

FROM v$archived_log GROUP BY applied;

The standby database is in sync with the primary database if the above PRIMARY value matches the above STANDBY value where applied = ‘YES’.

1. Learn to Say No and/or Delegate

Whether you’re addicted to doing everything yourself, or if you just have a hard time letting go, successful managers and leaders learn to accept that there are simply not enough hours to do it all. You can effectively increase your hourly pay if you can reduce your workload by delegating tasks to other members of your team. This can help to free up time to enjoy more personal and family activities without decreasing your salary. (Just be careful not to delegate the wrong things.)

2. Learn a Specialized Skill

Sometimes having a specialized, highly desirable skill set can make you more valuable to your employer. Find out what skills are most valuable in your industry and decide whether it’s something you can easily acquire in your spare time or whether your employer will help pay for you to acquire the skill. It could be learning HTML, learning the latest networking technology in the IT sector, or becoming a six-sigma black-belt. Previous employers of mine helped me to learn specific software programs like Adobe InDesign and Photoshop which increased my productivity (and in turn enhanced my worth to the company).

3. Earn a Higher Degree or Qualification

In some job sectors, merely having a certain degree, certificate or specialized training puts you in a higher pay scale. This can be more labor intensive, time consuming, and financially challenging, so be careful about how you navigate the pursuit of more formal education to improve your earning potential. Some employers will help pay for courses that are directly relevant to your current work, so it may be possible to pursue a part-time evening program and not decrease your earnings while you do it. This option is actually more work in the short term, but could have the most benefits over the long term. Many higher management jobs have minimum qualifications of a college degree or even an MBA. If that’s a job you’re aiming for, think about the best way to achieve that given your own circumstances.

4. Telecommute or Change Your Hours

If your employer is unwilling or unable to give you a raise for the incredible amount of work you do, they may be willing to adjust your hours or allow a telecommuting option, depending on the nature of your work. This doesn’t work for many industries, but if you’re in a job where you can complete most of your tasks from home, it may be worth asking if you can have a regular ‘work from home’ day once a week, or twice a month.

Alternatively, if you regularly stay late at the office, say 8 or 9 pm more than two or three times a week, ask if you can come in to the office at 10am or 11am instead of 8am or 9am. Your employer is still getting 40+ hours from you, but it will free up your mornings to have a workout, take the kids to school (if you have them), and do some personal chores. If you’re more productive in the mornings and would rather be home for dinner with your family, the reverse might be an option — suggest you come into the office at 6 or 7am instead of the normal 8 or 9am so you can leave by 3 or 4.

5. Become a Consultant rather than a Full-timer

If you regularly work well above and beyond the 40 hour work week, you might consider whether becoming an hourly consultant to your company makes more sense for you financially. It may not technically be less work, but it will be more flexible — and you can take on additional clients when you need the extra income rather than working 80 hours for the same employer without getting paid overtime.

6. Get a Raise for Work You Are Already Doing

If you’re the type of person that’s able to document significant increases in profit that you’ve brought to your company, or you’ve been doing way more than you were hired to do, you might be able to ask for a raise based on prior performance. If you can’t document significant outcomes (not outputs) that improved the company’s bottom line, consider what you need in order to do so — when your employer knows exactly how valuable you are to the company, it makes more business sense to invest in your personal happiness to keep you around.

7. Increase Your Productivity

If you find yourself repeating certain tasks on a regular basis, spend a portion of your day finding more efficient ways to complete them. For instance, in a previous job I was responsible for maintaining press lists for all the reporters in our research area. When I first became in charge of this task, I manually entered in phone numbers and email addresses for members of the press and would regularly make calls to ensure I still had correct contact information for distributing press releases. Eventually we subscribed to a service that maintained up to date press lists on our behalf. The service wasn’t free, but removing that task from my schedule increased my productivity and allowed me to focus my efforts on more important and valuable aspects of my job. There are thousands of companies out there trying to make you more efficient at your job — so spend some time investigating options for tasks that are repetitive.

8. Change Job

When all else fails and there’s not a way to transition into a healthier work-life balance at your current company, consider finding a new work environment where your skills and experience are more highly valued.

The bottom line is this: If your overworked and underpaid, you’ll head toward burnout quickly. Find a way to create more balance and earn more money for doing less (or the same) amount of work. These are a few tips to get there, but we’re always eager to hear what’s worked and what hasn’t work for your specific situation. Leave a comment below and start the conversation!

(Src: http://whitneymayparker.com)

• In Oracle Database 10g, by default, all tablespaces have built-in alerts that notify you when the free space in the tablespace goes below a certain predetermined threshold level.
• By default, Oracle sends out a warning alert when your tablespace is 85 percent full and a critical alert when the tablespace is 97 percent full. This also applies in the undo tablespace.
• If you are migrating to Oracle Database 10g, Oracle turns off the automatic tablespace alerting mechanism by default.

Tablespace Alerts Limitations

• You can set alerts only for locally managed tablespaces.
• When you take a tablespace offline or make it read-only, you must turn the alerting mechanism off.
• You will get a maximum of only one undo alert during any 24-hour period.

Using the Database Control to Manage Thresholds

Manage Metrics link | click the Edit Thresholds button

Using the DBMS_SERVER_ALERT Package

You can use the procedures: SET_THRESHOLD and GET_THRESHOLD in the DBMS_SERVER_ALERT package to manage database thresholds.

Examples:

To set your own databasewide default threshold values for the Tablespace Space Usage metric:

EXECUTE DBMS_SERVER_ALERT.SET_THRESHOLD(

METRICS_ID=>DBMS_SERVER_ALERT.TABLESPACE_PCT_FULL,

WARNING_OPERATOR=>DBMS_SERVER_ALERT.OPERATOR_GE,

WARNING_VALUE=>80,

CRITICAL_OPERATOR=>DBMS_SERVER_ALERT.OPERATOR_GE,

CRITICAL_VALUE=>95,

OBSERVATION_PERIOD=>1,

CONSECUTIVE_OCCURRENCES=>1,

INSTANCE_NAME=>NULL,

OBJECT_TYPE=>DBMS_SERVER_ALERT.OBJECT_TYPE_TABLESPACE,

OBJECT_NAME=>NULL)

To set a warning threshold of 80% and a critical threshold of 95% on the EXAMPLE tablespace, use the same previous example except OBJECT_NAME parameter should take value of ‘EXAMPLE’

To turn off the space-usage tracking mechanism for the EXAMPLE tablespace:

EXECUTE DBMS_SERVER_ALERT.SET_THRESHOLD(

METRICS_ID=>dbms_server_alert.tablespace_pct_full,

WARNING_OPERATOR=>dbms_server_alert.operator_do_not_check,

WARNING_VALUE=>’0′,

CRITICAL_OPERATOR=>dbms_server_alert.operator_do_not_check,

CRITICAL_VALUE=>’0′,

OBSERVATION_PERIOD=>1,

CONSECUTIVE_OCCURRENCES=>1,

INSTANCE_NAME=>NULL,

OBJECT_TYPE=>dbms_server_alert.object_type_tablespace,

OBJECT_NAME=>’EXAMPLE’)

In Oracle Database 10g, you can use the new segment-shrinking capability to make sparsely populated segments give their space back to their parent tablespace.

Restrictions on Shrinking Segments

• You can only shrink segments that use Automatic Segment Space Management.
• You must enable row movement for heap-organized segments. By default, row movement is disabled at the segment level.

ALTER TABLE test ENABLE ROW MOVEMENT;

• You can’t shrink the following:
  • Tables that are part of a cluster
  • Tables with LONG columns,
  • Certain types of materialized views
  • Certain types of IOTs.
  • Tables with function-based indexes.
• In Oracle 10.2 you can also shrink:
  • LOB Segments
  • Function Based Indexes
  • IOT Overflow Segments

Segment Shrinking Phases

There are two phases in a segment-shrinking operation:

Compaction phase

During this phase, the rows in a table are compacted and moved toward the left side of the segment and you can issue DML statements and queries on a segment while it is being shrunk.

Adjustment of the HWM/releasing space phase

During the second phase, Oracle lowers the HWM and releases the recovered free space under the old HWM to the parent tablespace. Oracle locks the object in an exclusive mode.

Manual Segment Shrinking

Manual Segment Shrinking is done by the statement:

ALTER TABLE test SHRINK SPACE

You can shrink all the dependent segments as well:

ALTER TABLE test SHRINK SPACE CASCADE

To only compact the space in the segment:

ALTER TABLE test SHRINK SPACE COMPACT

To shrinks a LOB segment:

ALTER TABLE employees MODIFY LOB(resume) (SHRINK SPACE)

To shrink an IOT overflow segment belonging to the EMPLOYEES table:

ALTER TABLE employees OVERFLOW SHRINK SPACE

Shrinking Segments Using the Database Control

To enable row movement:

Follow the links: Schema, Tables, Edit Tables, then Options.

To shrink a table segment:

Follow the links: Schema, Tables, select from the Actions field Shrink Segments and click Go.

Using the Segment Advisor

Choosing Candidate Objects for Shrinking

The Segment Advisor, to estimate future segment space needs, uses the growth trend report based on the AWR space-usage data.

Follow the links:

Database Home page, Advisor Central in the Related Links, Segment Advisor.

Automatic Segment Advisor

Automatic Segment Advisor is implemented by the AUTO_SPACE_ADVISOR_JOB job. This job executes the DBMS_SPACE.AUTO_SPACE_ADVISOR_JOB_PROC procedure at predefined points in time.

When a Segment Advisor job completes, the job output contains the space problems found and the advisor recommendations for resolving those problems.

You can view all Segment Advisor results by navigating to the Segment Advisor Recommendations page. You access this page from the home page by clicking the Segment Advisor Recommendations link in the Space Summary section.

The following views display information specific to Automatic Segment Advisor:

• DBA_AUTO_SEGADV_SUMMARY: Each row of this view summarizes one Automatic Segment Advisor run. Fields include number of tablespaces and segments processed, and number of recommendations made.
• DBA_AUTO_SEGADV_CTL: This view contains control information that Automatic Segment Advisor uses to select and process segments.

You plan to create a table in a tablespace and populate it with data. So, you want to estimate its initial size. This can be achieved using Segment Advisor in the EM or its package DBMS_SPACE.

Estimating Object Size using EM

You can use the Segment Advisor to determine your future segment resource usage.

Follow these steps:

1. From the Database Control home page, click the Administration tab.
2. Under the Storage section, click the Tables link.
3. Click the Create button to create a new table.
4. You’ll now be on the Create Table page. Under the Columns section, specify your column data types. Then click the Estimate Table Size button.
5. On the Estimate Table Size page, specify the estimated number of rows in the new table, under Projected Row Count. Then click the Estimated Table Size button. This will show you the estimated table size.

Estimating Object Size using DBMS_SPACE

For example, if your table has 30,000 rows, its average row size is 3 and the PCTFREE parameter is 20. You can issue the following code:

set serveroutput on

DECLARE

V_USED NUMBER;

V_ALLOC NUMBER;

BEGIN

DBMS_SPACE.CREATE_TABLE_COST (

TABLESPACE_NAME => ‘USERS’,

AVG_ROW_SIZE => 30,

ROW_COUNT => 30000,

PCT_FREE => 5,

USED_BYTES => V_USED,

ALLOC_BYTES => V_ALLOC);

DBMS_OUTPUT.PUT_LINE(‘USED: ‘|| V_USED/1024 || ‘ KB’);

DBMS_OUTPUT.PUT_LINE(‘ALLOCATED: ‘|| V_ALLOC/1024 || ‘ KB’);

END;

The USED_BYTES represent the actual bytes used by the data. The ALLOC_BYTES represent the size of the table when it is created in the tablespace. This takes into account, the size of the extents in the tablespace and tablespace extent management properties.

If you want to make the estimation based on the column definitions (not average row size and PCTFREE):

set serveroutput on

DECLARE

UB NUMBER;

AB NUMBER;

CL SYS.CREATE_TABLE_COST_COLUMNS;

BEGIN

CL := SYS.CREATE_TABLE_COST_COLUMNS(

SYS.CREATE_TABLE_COST_COLINFO(‘NUMBER’,10),

SYS.CREATE_TABLE_COST_COLINFO(‘VARCHAR2′,30),

SYS.CREATE_TABLE_COST_COLINFO(‘VARCHAR2′,30),

SYS.CREATE_TABLE_COST_COLINFO(‘DATE’,NULL));

DBMS_SPACE.CREATE_TABLE_COST(‘USERS’,CL,100000,0,UB,AB);

DBMS_OUTPUT.PUT_LINE(‘USED: ‘|| UB/1024 || ‘ KB’);

DBMS_OUTPUT.PUT_LINE(‘ALLOCATED: ‘|| AB/1024 || ‘ KB’);

END;

Undo Advisor

The Undo Advisor helps you perform the following tasks:

• Set the undo retention period
• Set the size of the undo tablespace

To access the Undo Advisor in the Database Control:

Follow the links: Database Control home page, Administration, Undo Management button, the Undo Advisor button in the right corner.

Redo Logfile Size Advisor

The Redo Logfile Size Advisor will make recommendations about the smallest online redo log files you can use.

The Redo Logfile Size Advisor is enabled only if you set the FAST_START_MTTR_TARGET parameter.

Check the column OPTIMAL_LOGFILE_SIZE in V$INSTANCE_RECOVERY view to obtain the optimal size of the redo log file for your FAST_START_MTTR_TARGET setting.

To access the Redo Logfile Size Advisor:

1. Database Control home page, Administration, Under the Storage section, Redo Log Groups.
2. Select any redo log group, and then choose the Sizing Advice option from the Action drop-down list, Click Go

In Oracle Database 10g, when a transaction rolls back, the event is recorded in the view V$SESSION_LONGOPS, if the process takes more than six seconds. This view enables you to estimate when the monitored rollback process will finish.

SELECT TIME_REMAINING,

SOFAR/TOTALWORK*100 PCT

FROM V$SESSION_LONGOPS

WHERE SID = 9

AND OPNAME =’Transaction Rollback’

Managing the SYSAUX Tablespace

• Some Oracle features use SYSAUX in its operation.
• SYSAUX is mandatory in any database.
• SYSAUX cannot be dropped, renamed or transported.
• Oracle recommends that you create the SYSAUX tablespace with a minimum size of 240MB.

Creating SYSAUX

• DBCA creates it automatically and asks you about its configuration.
• Can be included in the manual database creation:

CREATE DATABASE mydb

USER SYS IDENTIFIED BY mysys

USER SYSTEM IDENTIFIED BY mysystem

..

SYSAUX DATAFILE ‘c:\..\sysaux01.dbf’ SIZE 500M

If you omit the SYSAUX clause, Oracle will create the SYSAUX tablespace automatically with their datafiles in location defined by the following rules:

• If you are using Oracle Managed Files (OMF), the location will be on the OMF.
• If OMF is not configured, default locations will be system-determined.
• If you include the DATAFILE clause for the SYSTEM tablespace, you must use the DATAFILE clause for the SYSAUX tablespace as well, unless you are using OMF.

You can use ALTER TABLESPACE command to add a datafile though.

Relocating SYSAUX Occupants

If there is a severe space pressure on the SYSAUX tablespace, you may decide to move components out of the SYSAUX tablespace to a different tablespace.

• Query the column SPACE_USAGE_KBYTES in the V$SYSAUX_OCCUPANTS to how much of the SYSAUX tablespace’s space each of its occupants is currently using.
• Query the column MOVE_PROCEDURE to obtain the specific procedure you must use in order to move a given occupant out of the SYSAUX tablespace.

SQL> exec dbms_wm.move_proc(‘DRSYS’);

Note: You can’t relocate the following occcupants of the SYSAUX tablespace: STREAMS, STATSPACK, JOB_SCHEDULER, ORDIM, ORDIM/PLUGINS, ORDIM/SQLMM, and SMC.

Renaming Tablespaces

In Oracle Database 10g, you can rename tablespaces:

ALTER TABLESPACE users RENAME TO users_new

Restrictions:

• Your compatibility level must be set to 10.0 or higher.
• You can’t rename the SYSTEM or SYSAUX tablespace, or offline tablespaces.
• If the tablespace is read-only, the datafile headers aren’t updated, although the control file and the data dictionary are.

Renaming Undo Tablespace

• If database started using init.ora file, Oracle retrieves a message that you should set value of UNDO_TABLESPACE parameter.
• If database started using spfile, Oracle will automatically write the new name for the undo tablespace in your spfile.

Specifying the Default Permanent Tablespace

During Database Creation

Use DEFAULT TABLESPACE clause in the CREATE DATABASE command

CREATE DATABASE mydb

…

DEFAULT TABLESPACE deftbs DATAFILE …

If DEFAULT TABLESPACE not specified, SYSTEM tablespace will be used.

Note: The users SYS, SYSTEM, and OUTLN continue to use the SYSTEM tablespace as their default permanent tablespace.

After Database Creation Using SQL

Use ALTER DATABASE command as follows:

ALTER DATABASE DEFAULT TABLESPACE new_tbsp;

Using the Database Control

1. Database Control home page, Administration, Storage Section, Tablespaces.
2. Edit Tablespace page, select the Set As Default Permanent Tablespace option in the Type section. Then click Apply.

Viewing Default Tablespace Information

SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES

WHERE PROPERTY_NAME=’DEFAULT_PERMANENT_TABLESPACE’

Temporary Tablespace Groups

A temporary tablespace group is a list of temporary tablespaces.

It has the following advantages:

• You define more than one default temporary tablespace, and a single SQL operation can use more than one temporary tablespace for sorting. This prevents large tablespace operations from running out of temporary space.
• Enables one particular user to use multiple temporary tablespaces in different sessions at the same time
• Enables the slave processes in a single parallel operation to use multiple temporary tablespaces

Creating a Temporary Tablespace Group

You implicitly create a temporary tablespace group when you specify the TABLESPACE GROUP clause in a CREATE TABLESPACE statement:

CREATE TEMPORARY TABLESPACE temp_old TEMPFILE

‘/u01/oracle/oradata/temp01.dbf’ SIZE 500M

TABLESPACE GROUP group1;

You can also create a temporary tablespace group by:

ALTER TABLESPACE temp_old

TABLESPACE GROUP group1

Note: If you specify the NULL or ” tablespace group, it is equivalent to the normal temporary tablespace creation statement (without any groups).

Setting a Group As the Default Temporary Tablespace for the Database

ALTER DATABASE DEFAULT TEMPORARY TABLESPACE group1

Assigning a Temporary Tablespace Group to Users

CREATE USER sam IDENTIFIED BY sam

DEFAULT TABLESPACE users

TEMPORARY TABLESPACE group1;

ALTER USER SAM TEMPORARY TABLESPACE GROUP2;

Viewing Temporary Tablespace Group Information

Use the following views:

• DBA_TABLESPACE_GROUPS
• DBA_USERS

Bigfile Tablespaces

• A bigfile tablespace (BFT) contains only one very large file (can be as large as 8 to 128 terabytes depending on block size).
• The main benefit is easier management of tablespaces and their datafiles in very large databases (VLDB). All operations that were performed on data files in previous releases can now be performed on BFT tablespaces. For example: ALTER TABLESPACE … RESIZE

Big File Teblespaces Restrictions

• You use bigfile tablespaces along with a Logical Volume Manager (LVM) or the Automatic Storage Management (ASM) feature, which support striping and mirroring.
• Both parallel query execution and RMAN backup parallelization would be adversely impacted, if you used bigfile tablespaces without striping.
• You cannot change tablespace type from smallfile to bigfile or vice versa. However, you can migrate object between tablespace types by using either the ALTER TABLE … MOVE or CREATE TABLE … AS
• To avoid performance implications, use the following table as a guide to the maximum number of extents for a BFT with specific block size. If the expected size requires more extents than specified in the table, you can create the tablespace with UNIFORM option (instead of AUTOALLOCATE) with a large extend size.

Making Bigfile the Default Tablespace Type

Once you set the default type of your tablespace, all the tablespaces you subsequently create will be by default of the bigfile type:

CREATE DATABASE test

SET DEFAULT BIGFILE TABLESPACE … ;

ALTER DATABASE SET DEFAULT BIGFILE TABLESPACE;

You can view the default tablespace type using the following command:

SELECT PROPERTY_VALUE

FROM DATABASE_PROPERTIES

WHERE PROPERTY_NAME=’DEFAULT_TBS_TYPE’

Creating a Bigfile Tablespace Explicitly

CREATE BIGFILE TABLESPACE bigtbs

DATAFILE ‘/u01/oracle/data/bigtbs_01.dbf’ SIZE 100G …

When you use the BIGFILE clause, Oracle will automatically create a locally managed tablespace with automatic segment-space management (ASSM).

You can use the keyword SMALLFILE in replacement with BIGFILE clause.

Altering a Bigfile Tablespace’s Size

ALTER TABLESPACE bigtbs RESIZE 120G;

ALTER TABLESPACE bigtbs AUTOEXTEND ON NEXT 20G;

Viewing Bigfile Tablespace Information

All the following views have the new YES/NO column BIGFILE:

• DBA_TABLESPACES
• USER_TABLESPACES
• V$TABLESPACE

Bigfile Tablespaces and ROWID Formats

For bigfile tablespaces, there is only a single file, with the relative file number always set to 1024.

The only supported way to extract the ROWID components is by using the DBMS_ROWID package.

You can specify the tablespace type by using the new parameter TS_TYPE_IN, which can take the values BIGFILE and SMALLFILE.

SELECT DISTINCT DBMS_ROWID.ROWID_RELATIVE_FNO (rowid,’BIGFILE ‘) FROM test_rowid

Note: The functions DATA_BLOCK_ADDRESS_FILE and DATA_BLOCK_ADDRESS_BLOCK in the package DBMS_UTILITY do not return the expected results with BFTs.

Bigfile Tablespaces and DBVERIFY

You cannot run multiple instances of DBVERIFY utility in parallel against BFT. However, integrity-checking parallelism can be achieved with BFTs by starting multiple instances of DBVERIFY on parts of the single large file. In this case, you have to explicitly specify the starting and ending block addresses for each instance.

dbv FILE=BFile1 START=1 END=10000

dbv FILE=BFile1 START=10001

Viewing Tablespace Contents

You can obtain detailed information about the segments in each tablespace using Enterprise Manager.

On the Tablespaces page, select the tablespace of interest, choose Show Tablespace Contents from the Actions drop-down list, and click Go. The Processing: Show Tablespace Contents page is displayed.

Sorted hash clusters are new data structures that allow faster retrieval of data for applications where data is consumed in the order in which it was inserted.

In a sorted hash cluster, the table’s rows are already presorted by the sort key column.

Here are some of its main features:

• You can create indexes on sorted hash clusters.
• You must use the cost-based optimizer, with up-to-date statistics on the sorted hash cluster tables.
• You can insert row data into a sorted hash clustered table in any order, but Oracle recommends inserting them in the sort key column order, since it’s much faster.

Creating Sorted Hash Cluster

CREATE CLUSTER call_cluster

(call_number NUMBER,

call_timestamp NUMBER SORT,

call_duration NUMBER SORT)

HASHKEYS 10000

SINGLE TABLE

HASH IS call_number

SIZE 50;

CREATE TABLE calls

(call_number NUMBER,

call_timestamp NUMBER,

call_duration NUMBER,

call_info VARCHAR2(50))

CLUSTER call_cluster

(call_number,call_timestamp,call_duration)

The following are the newly supported options for partitioned index-organized tables (IOTs):

• List-partitioned IOTs: All operations allowed on list-partitioned tables are now supported for IOTs.
• Global index maintenance: With previous releases of the Oracle database, the global indexes on partitioned IOTs were not maintained when partition maintenance operations were performed. After DROP, TRUNCATE, or EXCHANGE PARTITION, the global indexes became UNUSABLE. Other partition maintenance operations such as MOVE, SPLIT, or MERGE PARTITION did not make the global indexes UNUSABLE, but the performance of global index–based access was degraded because the guess–database block addresses stored in the index rows were invalidated. Global index maintenance prevents these issues from happening, keeps the index usable, and also maintains the guess–data block addresses.
• Local partitioned bitmap indexes: The concept of a mapping table is extended to support a mapping table that is equi-partitioned with respect to the base table. This enables the creation of bitmap indexes on partitioned IOTs.
• LOB columns are now supported in all types of partitioned IOTs.

The package DBMS_REDEFINITION is known to be used as a tool to change the definition of the objects while keeping them accessible (online). In previous versions, if you use it to move a partitioned table to another tablespace, it will move the entire table. This results in massive amount of undo and redo generation.

In Oracle 10g, you can use the package to move a single partition (instead of the entire table). The following code illustrates the steps you follow.

1. Confirm that you can redefine the table online. Having no output after running the following code means the online redefinition is possible:

BEGIN

DBMS_REDEFINITION.CAN_REDEF_TABLE(

UNAME => ‘HR’,

TNAME => ‘customers’,

OPTIONS_FLAG => DBMS_REDEFINITION.CONS_USE_ROWID,

PART_NAME => ‘p1′);

END;

1. Create a temporary (interim) table to hold the data for that partition:

CREATE TABLE hr.customers_int

TABLESPACE custdata

AS

SELECT * FROM hr.customers

WHERE 1=2;

Note: If the table customers had some local indexes, you should create those indexes (as non-partitioned, of course) on the table customers_int.

1. Start the redefinition process:

BEGIN

DBMS_REDEFINITION.START_REDEF_TABLE(

UNAME => ‘HR’,

ORIG_TABLE => ‘customers’,

INT_TABLE => ‘customers_int’,

PART_NAME => ‘p1′ ); — partition to move

END;

1. If there were DML operations against the table during the move process, you should synchronize the interim table with the original table:

BEGIN

DBMS_REDEFINITION.SYNC_INTERIM_TABLE (

UNAME => ‘HR’,

ORIG_TABLE => ‘customers’,

INT_TABLE => ‘customers_int’,

COL_MAPPING => NULL,

OPTIONS_FLAG => DBMS_REDEFINITION.CONS_USE_ROWID,

PART_NAME => ‘p1′ );

END;

1. Finish the redefinition process:

BEGIN

DBMS_REDEFINITION.FINISH_REDEF_TABLE (

UNAME => ‘HR’,

ORIG_TABLE => ‘customers’,

INT_TABLE => ‘customers_int’,

PART_NAME => ‘p1′);

END;

To confirm the partition P1 was moved to the new tablespace:

SELECT PARTITION_NAME, TABLESPACE_NAME, NUM_ROWS

FROM USER_TAB_PARTITIONS

WHERE PARTITION_NAME=’P1′

Note: If there is any global index on the table, they will be marked as UNUSABLE and must be rebuilt.

Note: You cannot change the structure of the table during the definition process.

Note: statistics of object moved with this tool are automatically generated by end of the process.

The DBMS_FILE_TRANSFER package helps you copy binary files to a different location on the same server or transfer files between Oracle databases.

Both the source and destination files should be of the same type, either operating system files or ASM files.

The maximum file size is 2 terabytes, and the file must be in multiples of 512 bytes.

You can monitor the progress of all your file-copy operations using the V$SESSION_LONGOPS view.

Copying Files on a Local System

CREATE DIRECTORY source_dir AS ‘/u01/app/oracle’;

CREATE DIRECTORY dest_dir AS ‘/u01/app/oracle/example’;

BEGIN

DBMS_FILE_TRANSFER.COPY_FILE(

SOURCE_DIRECTORY_OBJECT => ‘SOURCE_DIR’,

SOURCE_FILE_NAME => ‘exm_old.txt’,

DESTINATION_DIRECTORY_OBJECT => ‘DEST_DIR’,

DESTINATION_FILE_NAME => ‘exm_new.txt’);

END;

Transferring a File to a Different Database

BEGIN

DBMS_FILE_TRANSFER.PUT_FILE(

SOURCE_DIRECTORY_OBJECT => ‘SOURCE_DIR’,

SOURCE_FILE_NAME => ‘exm_old.txt’,

DESTINATION_DIRECTORY_OBJECT => ‘DEST_DIR’,

DESTINATION_FILE_NAME => ‘exm_new.txt’

DESTINATION_DATABASE => ‘US.ACME.COM’);

END;

In order to transfer a file the other way around, you must replace the PUT_FILE procedure with the GET_FILE procedure.

If you are copying a database datafile, do not forget to make it READ ONLY before you start to copy.

You can monitor copying progress using V$SESSION_LONGOPS view.

In previous versions, if you drop a partitioned table, Oracle removes all the partitions at once. This led to a time and resource consuming process.

In Oracle Database 10g Release 2, when you drop a partitioned table, partitions are dropped one by one. Because each partition is dropped individually, fewer resources are required than when the table is dropped as a whole.

In Oracle 10g release 2, empty datafiles can be dropped

ALTER TABLESPACE test DROP DATAFILE ‘hr1.dbf’;

You cannot drop non-empty datafiles

ORA-03262: the file is non-empty

You cannot drop first file in tablespace

ORA-03263: cannot drop the first file of tablespace HR

In Oracle 10.2 temporary files can be renamed.

ALTER DATABASE TEMPFILE ‘temp1.dbf’ OFFLINE

$ mv temp1.dbf temp2.dbf

ALTER DATABASE RENAME FILE ‘temp1.dbf’ TO ‘temp2.dbf’

ALTER DATABASE TEMPFILE ‘temp1.dbf’ ONLINE

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Vietnamese food is quite unlike any other food in Southeast Asia. It’s even quite different from China. Overall it’s a blend of Malay, Indian, French and influences and incorporates baguettes and pate from France; and curries and chilies from India.

Recently voted by health experts as the world’s healthiest food, Vietnamese cuisine mixes grilled meats, fresh vegetables, cold noodles, and all kinds of seafood dishes spiced with tamarind and chili.
Available at all hours of the day, Vietnamese food can be eaten as snacks, in street side stalls, in budget restaurants, and in hotels. In many cases only the price is the difference because often the tastiest foods come from the most basic kitchens.
As you travel up or down the country, you will notice sharp differences in both main dishes and snacks eaten by locals. Its one of the joys of traveling in the country, and it’s a good idea to ask your guide to point out interesting things to eat.
THE NORTH
With the weather so cold for so much of the year, soups play a large part in Northern  cuisine. Pho, Vietnam’s ‘chicken soup,’ is made with white vermicelli noodles, sliced beef or chicken, bean sprouts, chopped peanuts, hot broth and mint leaves that is served piping hot and at all hours of the day. Pho stalls can be found all over Hanoi (and Hanoi style Pho can be found all over Vietnam, catering to homesick Hanoians) and a bowl can cost between 5,000 and 10,000 dong, depending on the location.
Once the bowl is put in front of you, spice it up with bean sauce and chili sauce and squeeze in a few lime wedges; then dig in with a pair of chopsticks in one hand (to lift up the noodles to cool them off) and a spoon in the other (to lift the noodles to your mouth). Other soups include Chao, a kind of rice porridge, and it’s often prescribed as a remedy for common colds.
By far the favorite food in Hanoi is ‘Bun Cha’ grilled meat eaten at makeshift restaurants serving patrons on the street. It’s a great way to fill up for just a few thousand dongs, and when walking around the city it may be impossible to resist the smell.
Bia Hoi is a Hanoi invention, and ‘Bia’ comes from the English word ‘beer.’ Its freshly brewed and served in plastic jugs; its cheap, and it’s a great way to soak up Hanoi’s ambiance at night and you might even make some friends along the way.
Hanoians may be a reserved bunch, but they are downright adventurous when it comes to exotic food: fried silk worms, cobra meat, dog meat among others are eaten by people in the capital to cure sickness, increase virility or just because it’s the right season.

THE CENTER
Most of the food eaten in Central Vietnam has some link to the imperial kitchens of the Nguyen Emperors in Hue. Many of the spices, techniques and vegetables come straight from the tables of the emperors themselves.
Imperial spring rolls are commonly eaten, as is Bun Bo Hue, a spicy beef soup that is not for the faint hearted; you may need a bottle of water nearby to wash down the chili peppers.
Perhaps the most famous is Banh Khoai, a pancake like food that is eaten with nuoc leo, a rich peanut sauce. The pancake includes eggs, shrimps and bean sprouts (much like Banh Xeo, in the south, discussed later)
A popular snack is Banh Beo, tiny ceramic dishes with a boiled rice cake topped with pork bits and eaten with a spoon; Drop a small amount of fish sauce (Nuoc Mam) on top and dig in.
A lot of seafood is eaten here as well, and boiled crabs are a specialty.
Perhaps the most exotic food eaten here is Com Hen, a cold rice dish flavored with juice from clams that live in the river near Hoi An. Other ingredients include white vermicelli noodles, chili and shrimp sauce. Its quite a difficult dish to prepare and is not for those who worry about healthy shellfish.
THE SOUTH
The South of Vietnam is considered to have the best food in the country, namely because Saigon, with its increasingly wealthy inhabitants, demand the highest quality vegetables fruits meats etc, and foreign foods (even American Fast Food giants KFC are here) are increasingly common from French to Mexican to Indian.
With the lush Mekong Delta so close, the fruit is very fresh, pineapple, mango and star fruit all come into play in dishes as they come into season.
Banh Xeo is perhaps the most famous Southern Dish, like Banh Khoai, it too is a pancake, but the dish Banh Xeo is much larger, and uses more green beans, shrimps and coconut milk. It serves more than one person, and is dipped in nuoc mam, fish sauce, after being wrapped in fresh lettuce leaves.
Freshly cooked spring rolls are famous in Saigon, but the most specialized are Goi Cuon, the fresh spring rolls combining sliced cold shrimp, mint leaves, cold vermicelli noodles, and rice paper that is dipped in nuoc mam.
Some Southern exotics include Hot Vit Lon, or fertilized duck egg, that is eaten with a spoon and is usually available in markets and street stalls.

——————-

Com (boiled rice)
In Vietnam, com is eaten at the main meals of the day (lunch and dinner). Rice is eaten together with a variety of different dishes and is made from different kinds of rice. Typically fragrant rice is used, such as Tam Thom and Nang Huong. An ordinary meal may consist of boiled rice and the following:
Mon an kho (meal without soup) consists of dishes of pork, fish, shrimp, and vegetable cooked in oil, as well as vegetables, pickles, etc.
Mon canh (meal with soup) consists of a soup made with pork or spare-ribs, crab meat, and fish.
In the past several years, people in urban centers have begun to go out for lunch at the food stalls on the street. Consequently, there has been a proliferation of temporary food stalls along many sidewalks and public spaces in the cities. Some stalls are open until early in the morning to cater to regular customers. Around noon, owners can be seen arranging tables and benches along the pavement to form makeshift shop floors. After two or three hours, when there are no more customers, they begin to remove all of their wooden furniture, so that the place resumes its former appearance. A well served lunch for one is very inexpensive.
——————————————————————————–
Banh Chung (Sticky Rice Cake)
Sticky rice cakes are a Vietnamese traditional dish that must be part of Tet meals. As a matter of fact, every Vietnamese family must have sticky rice cakes among the offerings placed on the altar to their ancestors.
Bang chung is made of glutinous rice, pork meat, and green beans paste wrapped in a square of bamboo leaves, giving the rice a green colour after boiling.
According to the legend, under the reign of the Hung Kings, Prince Lang Lieu created sticky rice cakes and presented them to his father. Bang chung won high acclaims from the King who awarded the prince his throne.
Making sticky rice cakes is a very meticulous job. To obtain the best cakes, rice has to soak in water for an entire day. The pork meat must include skin and fat, the green beans must be of the same size, and the bamboo leaves must be fresh. Squaring off and tying cakes with bamboo strings requires skilful hands.
Sticky rice cakes are available at any time of the year, although one is sure to enjoy them with relatives and friends during Tet. During Tet, rice cakes are served with gio lua and hanh muoi– lean meat pie and salted sour onions.
——————————————————————————–
Gio Lua (Lean Pork Pie)
Lean pork pie is available in Vietnam only and has different names in the north and south. Foreigners as well as Vietnamese are fond of lean pork pie.
Gio lua consists of pork meat wrapped in fresh banana leaves. The little bundles are then boiled. The most delicious part of lean pork pie is the top layer since it absorbs the flavour of the banana leaves.
——————————————————————————–
Pho – Noodles
Pho is the most popular food among the Vietnamese population. Pho is commonly eaten for breakfast, although many people will have it for their lunch or dinner. Anyone feeling hungry in the small hours of the morning can also enjoy a bowl of hot and spicy pho to fill their empty stomachs.
Like hot green tea which has its particular fragrance, pho also has its special taste and smell. Preparations may vary, but when the dish is served, its smell and taste is indispensable. The grated rice noodle is made of the best variety of fragrant rice called Gao Te. The broth for Pho Bo (Pho with beef) is made by stewing the bones of cows and pigs in a large pot for a long time. Pieces of fillet mignon together with several slices of ginger are reserved for Pho Bo Tai (rare fillet). Slices of well done meat are offered to those less keen on eating rare fillets.
The soup for Pho Ga (pho with chicken meat) is made by stewing chicken and pig bones together. The white chicken meat that is usually served with Pho Ga is boneless and cut into thin slices. You could consider Pho Bo and Pho Ga Vietnam’s special soups. Pho also has the added advantage of being convenient to prepare and healthy to eat.
——————————————————————————–
Cha Ca (grilled minced fish)
Grilled minced fish has been served in Vietnam for more than 100 years. The Doan family of Cha Ca Street in Hanoi first invented this dish.
A wide variety of fish can be used in this dish including sturgeon and tuna. Tuna is low in fat, has an exquisite flavour, and few bones. The bones are separated from the meat and put into saffron water to be later used in a sauce. The fish is marinated in salt before being grilled.
What is interesting about this dish is that people can add their favourite condiments: coriander, mint, dill, shallots, and more.
——————————————————————————–
Com (Grilled rice)
Grilled rice is mostly served in the fall. After collecting the rice from the fields, several steps have to be performed to obtain excellent com. After removing the grains from their hulks, the rice is wrapped in lotus leaves to keep it from drying and to allow it to absorb the lotus flavor.
Grilled rice can be found everywhere in Vietnam, but the best com is found in Vong village, 5 km from Hanoi. People in this village still use traditional secret recipes. People eat grilled rice with eggs, bananas, or sapodillas.
——————————————————————————–
Banh Cuon (Rice Flour Steamed Rolls)
Eating banh cuon for breakfast is a great favorite among many Vietnamese.
Banh cuon is made of rice flour. Thoroughly selected rice is soaked overnight, then ground with a stone mortar. Food preservatives are put into the flour to make the rice sheets softer and smoother. A screen of cloth used to mold the rice sheets is fitted over the opening of a pot of boiling water. Flour is spread on the screen and covered with a lid. After a few minutes, a bamboo stick is used to strip the thin layer of flour off the screen. Then it is rolled up and sprinkled with fried onions.
A small village in a suburb of Hanoi is famous for its banh cuon. People there serve it with a dressing comprised of lean meat, shrimps, mushrooms, dried onions, fish sauce, and pepper.
All the ingredients are stir-fried and rolled into a banh cuon.
Banh cuon is delicious when it is very thin, white, and sticky. It is even tastier when dipped in a sweet, sour, and spicy sauce.
——————————————————————————–
Bun (rice vermicelli)
Vietnamese vermicelli is a luxurious as well as a popular dish. There are different varieties of vermicelli depending on their shape: bun roi or stirred vermicelli, bun mam or twisted vermicelli, bun la or vermicelli paper, and bun dem tram or shreded vermicelli.
Different ingredients can be served with vermicelli: grilled pork meat, fried rice cakes, snails, fried eggs, lean meat pie, chicken, and crab soup, to name a few.
Each region and locality, even each restaurant, has its own vermicelli dishes with their own recipes.
——————————————————————————–
Mien (vermicelli made of cassava)
Mien threads are very long and tough, made from a kind of tuber plant called cassava. When served, the long tiny flour threads are cut into smaller pieces. Like rice vermicelli, this kind of cassava vermicelli is used to make several different dishes, the most popular being Mien Ga (chicken cassava vermicelli), Mien Bo (beef cassava vermicelli), and Mien Luon (eel cassava vermicelli).
Cassava vermicelli is also used for different dishes which are stirred in oil, such as Mien Xao Thit (vermicelli and pork stirred in fat), Mien Xao Long Ga (vermicelli and chicken tripe stirred in fat), and Mien Xao Cua Be (vermicelli and sea crab meat stirred in fat).
——————————————————————————–
Banh Tom (crispy shrimp pastry)
Although Banh Tom is available almost everywhere in the country, it is best at the Nha Hang Ho Tay (Ho Tay Restaurant) on the banks of Truc Bach Lake, close to Ho Tay (West Lake) in Hanoi. While diners await the arrival of the hot fried shrimp pastry, they can enjoy the picturesque lake and landscapes offered by the vast expanse of water from West Lake and the tree-lined Thanh Nien Road.
The dish should be eaten as soon as it arrives at the table. The fried pastry is topped with red shrimps and is eaten together with dishes of spicy vegetables mixed with sweet and sour sauce.
To remind you of the local shrimping business, waiters will often tell you that the shrimps that you have ordered for your meal have just been netted in nearby West Lake. This will be a memorable meal that will ensure that you remember your stay in Hanoi.
——————————————————————————–
Nom (salad)
This dish is a combination of a variety of fresh vegetables, usually used in salads in Western countries. The make-up of Nom, however, is slightly different.
The main ingredients of Nom include grated pieces of turnip, cabbage, or papaya, and slices of cucumber with grated, boiled, lean pork. Other auxiliary ingredients include grated carrot, slices of hot chilly, and roasted ground nuts. These are used to make the dish more colourful. All are mixed thoroughly before being soaked in vinegar, sugar, garlic, hot chilly, and seasoned with salt.
The presentation of the dish is also very meticulous. The mixture of ingredients is put into a dish before being covered with vegetables.
To try a mouthful of Nom is to enjoy a combination of all the tastes life has to offer, including sour, hot, sweet, salty, and fragrant tastes. The dish helps with digestion at meals and parties. It can become an addictive aid to assist the real connoisseur enjoy more food.
——————————————————————————–
Nem Ran or Cha Gio (fried spring roll)
This dish is called Nem Ran by northerners and Cha Gio by southerners. In Hanoi, the introduction of Nem Ran dates back to a time when Cha Ca had not existed. Although it ranks among Vietnam’s specialty dishes, Nem Ran is very easy to prepare. Consequently, it has long been a preferred food on special occasions such as Tet and other family festivities.
Ingredients used for Nem Ran comprise of lean minced pork, sea crabs or unshelled shrimps, two kinds of edible mushroom (Nam Huong and Moc Nhi), dried onion, duck eggs, pepper, salt and different kinds of seasoning. All are mixed thoroughly before being wrapped with transparent rice paper into small rolls. These rolls are then fried in boiling oil.
——————————————————————————–
Faifo Dainty (Danang)
Faifo dainty is a fairly unknown Vietnamese dish named after an old street in Hoi An.
Dainty fiber is carefully made by putting rice in water containing ashes from wood found in Cu Lao Cham. Then, the rice is ground and quickly boiled to make a fibrous mixture. Dainty can be preserved only one day, which is why it is boiled and dried. Dainty fibers have a dark-yellow colour.
The filling for dainty consists of lean pork and other condiments that are stir-fried. Then, the dainty is cut into finger-long pieces that are dried and grilled. Finally, the filling is put into the dainty. For a saltier taste, one can add fish sauce. Chicken meat cut in squares combined with small shrimps can also be added to the recipe.
Although dainty is not a popular meal in Vietnam, it is still served in certain restaurants in Ho Chi Minh City.
——————————————————————————–
Tom Chua (Hue Sour Shrimp)
When Hue natives living outside the city return to their homeland, they usually have sour shrimp. Tourists also make sure to buy some jars of sour shrimp before leaving Hue.
Because of the national reputation of this dish, some cooks and merchants specialize in making sour shrimp. In the past, people made this dish at home, but now it is easier to buy it at the market.
This dish can be prepared with any kind of shrimp. The recipe includes a number of steps that must be performed in a specific order. First, the fresh, clean, and dry shrimp of approximately the same size are put in wine along with dry bamboo shoots, garlic, and chili. The ingredients are kept in a closed container at room temperature for three days. Then the container is put in a cool, dry place. After five or seven days, the sour shrimp are ready.
——————————————————————————–
Com Hen (Hue Mussel Rice)
Hot white rice is part of every meal in Vietnam, but only Hue mussel rice is served cool. Hue people, after deciding that no food should be wasted, have designed this dish using leftover rice.
This dish includes Chinese vermicelli, bamboo shoots, lean pork meat, and an assortment of green vegetables (banana leaves, mint, star fruit, etc.).
The broth obtained after boiling the mussels is used to flavour the rice. Ginger, sesame, and chili are also added to the broth. This dish is very spicy and it is not rare to see people with watery eyes and sweaty faces while eating it; nevertheless, everyone congratulates the cook for such a delicious meal.
——————————————————————————–
Hue Beef Noodle Soup
One must have years of experience to cook excellent Hue beef noodle soup. This recipe mainly consists of shredded meat and rice noodles. Most restaurants and merchants in Hue do not make the rice noodles themselves; they buy them in Van Cu and Bao Vinh, two villages located near Hue.
Learning how to make a clear broth from bone and meat is also a difficult task, but cooks have the satisfaction of seeing customers enjoying a good meal. The secret of this recipe resides in the meat–this is why it must be bought directly from the slaughterhouse early in the morning. The meat is then shredded, boiled, and taken out of the water to obtain a delicious clear broth.
The amount of salt put in the recipe varies depending on the season; during summer, Hue beef noodle soup is served with soy bean, mint, and different kinds of lettuce; in the winter, the recipe is saltier and lemongrass and fish sauce are added.
——————————————————————————–
Cau Mong Beef
Cau Mong beef is a specialty of Cau Mong, located 15 km from Danang, Dien Ban district, where nearly ten restaurants serve the dish. Cau Mong beef has been served for a long time and is found in many places outside Danang, such as Hoi An, Tam Ky, Vinh Dien, and Ho Chi Minh City.
The meat along with its skin is cut in thin slices, half cooked, and eaten with nem, which consists of fish sauce mixed with soy sauce, sugar, chili, garlic, lemon, star fruit, vervain, and green banana.
——————————————————————————–
Hu Tieu (My Tho Noodle Soup)
My Tho seafood noodle soup is different from Chinese noodle soup, nam vang soup, and Hue beef noodle soup, because it contains soy bean, lemon, chili, and soy sauce instead of herbs and lettuce.
Back in the 1960s, a shop in My Tho, 70 km from Ho Chi Minh City, started serving this dish using a secret recipe for the rice noodles. Ever since then, its reputation has grown to become a very well known meal in Vietnam.
It is said that the most delicious noodle soup is made with Co Cat rice, from the most famous rice growing area of My Phong village, a suburb of My Tho.
The sweet aroma of the broth comes from the meat, dried squid, and special condiments.
My Tho noodle soup is a traditional dish specific to the south.
——————————————————————————–
Lau Mam (Mixed Soup)
Lau mam was a popular dish among farming communities hundreds of years ago, especially in the southwestern provinces. Nowadays, lau mam is considered a delicacy and is often served to special guests. Lau designates the broth, and mam the salted fish.
The main ingredient used in the broth is marinated fish to which meat and vegetables are added. Various ingredients, such as seafood, fish, and meat, are prepared on separate plates. Guests choose and boil their meat in the broth. The meal is accompanied by several fresh vegetables and aromatic herbs.
This dish is particularly enjoyed since so many alternatives are possible, offering a wide array of delicious flavours.
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Canh Chua (Fish Sour Soup)
Canh chua originated from the Mekong Region, more specifically from Dong Thap Muoi. Canh chua is a fish sour soup made with fish from the Mekong River and so dua flower. This dish is mostly served when the so dua flower first blossoms at the end of the rainy season. A feast is organized and the fish sour soup is among the delicious meals prepared for this event. Fish sour soup must be eaten very hot. It must also be eaten all at one time since the taste is altered when the soup is reheated.
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Chao Tom (Grilled Shrimp Paste)
Foreigners often say that grilled shrimp paste is a very unusual dish made from very simple ingredients. The recipe consists of clean shrimps placed in coconut water. The shrimps are later grilled and ground to obtain shrimp flour. The flour is mixed with fat and sugar to finally obtain shrimp paste. This dish is served with fish sauce.
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Banh Cuon Trang Bang (Rice Cakes)
Trang Bang, located 40 km from Ho Chi Minh City, is where one can find the best rice paper and rice cakes.
Both can be found everywhere, but nowhere are they better than in Trang Bang where they are made from local rice. The rice flour is roasted for four or five hours and made into thick cakes. Once the cakes are dried, they are placed into nylon bags.
These cakes can be eaten with shrimp, meat, salad, and coriander. During Tet, the cakes are served with roasted meat, eggs, and sour mustard.

(Source: activetravelvietnam.com)

Spices and ingredients

Vietnam’s ingredients reflect its geography and climate. Rice (grown in water paddies throughout the country) is the main starch used in everyday meals, and is also made into different kind of cakes and noodles. Besides a number of Buddhist vegetarian dishes, most Vietnamese dishes or meals are a combination of a variety of vegetables, herbs and meats.

Common herbs may include lemon grass, lime or kaffir. Popular meats are pork, beef, chicken, prawn and various fish. Lamb, duck, birds, and even dog or other wild animals are also used but not widely. Fish sauce and soy sauce are used as both flavorings and dipping sauces for nearly every dish.

Peanuts are also used widely in Vietnamese cuisine.

Vegetarians and those with allergies should be careful and ask beforehand while enjoying Vietnamese cuisine.

Style of cooking

The Vietnamese cook their food in a variety of ways: deep fry, stir fry, boil, steam. Unlike the Chinese, the Vietnamese use a minimal amount of oil while cooking. Vietnamese cooks aim to preserve the freshness and natural taste of food as much as possible. Hence Vietnamese cuisine is often considered as one of the healthiest foods in the world.

Food of three regions

Like everything else, Vietnamese food also differs geographically from location to location. North Vietnam’s food uses soy sauce, fish sauce and prawn sauce and has many stir fried dishes.

With harsh weather and less developed agriculture than the South, North Vietnamese tend to use less meat, fish and vegetables; and black pepper (instead of chili) to create spice. The taste is strict and less sweet, but more salty than in other regions.

Central Vietnam is distinct in its extreme spices and color of food. Hue’s cuisine, affected by royal cuisine once created for kings and queens, emphasized on quality and quantity – A meal constitutes of many complex dishes served only at small proportions.

Southern Vietnamese are heavily affected by Cambodia, Thai and Chinese cuisines (due to trade and immigrants). Southerners prefer sweet tastes (created by adding sugar or coconut milk) and spicy tastes (created by chili peppers).

A variety of dried fish and sauces originate from the South. Southerners prefer seafood and use simple cooking methods with larger and less servings.

Customs

Influenced by the Chinese, chopsticks and spoons are used in Vietnam. Many foods (such as cakes) are wrapped in banana or coconut leaves. When eating with elders, younger Vietnamese always ask the elders to eat first.

A typical family meal

A typical Vietnamese meal (lunch or dinner) will include steamed rice; a soup dish to eat with rice, a meat or fish dish and a vegetarian dish (either stir fried or boiled).

Vietnamese do not eat in separate servings, but the food is placed in the middle. Each member of the family has a small bowl and chopsticks with which they take food from the table throughout the meal.

Vietnamese noodles and cakes

Besides the typical meal with rice, Vietnamese cuisine has many different types of noodles and cakes (mostly made from rice). To name a few: beef soup noodles (pho), crab noodle (bun rieu), spring rolls (nem), sticky rice cake (chung cake)…

* Source: guidevietnam.com

The High Watermark is the maximum fill-grade a table has ever reached.
Above the high watermark are only empty blocks.
These blocks can be formatted or unformatted.

First let’s have a look at the question when space is allocated

- when you create a table at least one extent (contiguous blocks) is allocated to the table
- if you have specified MINEXTENTS the number of MINEXTENTS extents
will be allocated immedaitely to the table
- if you have not specified MINEXTENTS then exactely one extent
will be allocated (we will look at extent sizes later in another post).

Immediately after creation of the segment (table) the high watermark will be at the first block of the first extent as long as there are no inserts made.

When you insert rows into the table the high watermark will be bumped up step by step.
This is done by the server process which makes the inserts.

Now let us take a look at when space is released again from a segment like a table or index:

Let’s asume that we have filled a table with 100’0000 rows.
And let’s asume that we deleted 50’000 rows afterwards.
In this case the high watermark will have reached the level of 100’000 and will have stayed there. Which means that we have empty blocks below the high watermark now.
Oracle has a good reason this: it might occur that you delete rows and immediately this you insert rows into the same table. In this case it is good that the space was not released with the deletes, because it had to be get reallocate again for the following inserts, which would mean permanent changes to the data dictionary
(=> dba_free_space, dba_extents, dba_segements …) .
Furthermore the physical addresses of the deleted row get recycled by new rows.

These empty blocks below the high watermark can get annoying in a number of situations because they are not used by DIRECT LOADs and DIRECT PATH LOADs:

1. seriell direct load:
INSERT /*+ APPEND */
INTO hr.employees
NOLOGGING
SELECT *
FROM oe.emps;

2. parallel direct load:
ALTER SESSION ENABLE PARALLEL DML;
INSERT /*+PARALLLEL(hr.employees,2)
INTO hr.employees
NOLOGGING
SELECT *
FROM oe.emps;

3. direct path loads:
sqlldr hr/hr control=lcaselutz.ctl … direct=y (default is direct=n)

All the above actions case that the SGA is not used for the inserts but the PGA:
there wil be temporary segements filled and dumped into newly formatted blocks above the high watermark.

So we might want to get high watermark down before we load data into the table in order to use the free empty blocks for the loading.

So how can we release unused space from a table?

There are a number of possible options which are already available before Oracle 10g:
- What we always could do is export and import the segment.
After an import the table will have only one extent.
The rows will have new physical addresses and
the high watermark will be adjusted.
- Another option would be to TRUNCATE the table.
With this we would loose all rows which are in the table.
So we cannot use this if we want to keep existing records.

With Oracle 9i another possibilty was implemented:
ALTER TABLE emp MOVE TABLESPACE users;
This statement will also cause that
- the rows will have new physical addresses and
- the high watermark will be adjusted.
But for this:
- we need a full (exclusive) table lock
- the indexes will be left with the status unusable (because they contain the old rowids) and must be rebuilt.

Starting with ORACLE 10gR1 we can use a new feature for adjusting the high watermark,
it is called segment shrinking and is only possible for segments which use ASSM, in other words, which are located in tablespaces which use Automatic Segement Space Management.
In such a tablespace a table does not really have a High watermark!
It uses two watermarks instead:
- the High High Watermark referred to as HHWM, above which alle blocks ar unformatted.
- the Low High Watermark referred to as LHWM below which all blocks are formatted.
We now can have unformatted blocks in the middle of a segment!

ASSM was introduced in Oracle 9iR2 and it was made the default for tablespaces in Oracle 10gR2.
With the table shrinking feature we can get Oracle
to move rows which are located in the middle or at the end of a segment
further more down to the beginning of the segment and by
this make the segment more compact.
For this we must first allow ORACLE to change the ROWIDs of these rows by issuing
ALTER TABLE emp ENABLE ROW MOVEMENT;
ROWIDs are normally assigned to a row for the life time of the row at insert time.

After we have given Oracle the permission to change the ROWIDs
we can now issue a shrink statement.
ALTER TABLE emp SHRINK SPACE;

This statement will procede in two steps:
- The first step makes the segment compact
by moving rows further down to free blocks at the beginning of the segment.
- The second step adjusts the high watermark. For this Oracle needs an exclusive table lock,
but for a very short moment only.

Table shrinking…
- will adjust the high watermark
- can be done online
- will cause only rowlocks during the operation and just a very short full table lock at the end of the operation
- indexes will be maintained and remain usable
- can be made in one go
- can be made in two steps
(this can be usefull if you cannot get a full table lock during certain hours:
you only make the first step and adjust the high watermark later
when it is more conveniant:

- ALTER TABLE emp SHRINK SPACE; – only for the emp table
- ALTER TABLE emp SHRINK SPACE CASCADE; – for all dependent objects as well

- ALTER TABLE emp SHRINK SPACE COMPACT; – only makes the first step (moves the rows)
)

How are the indexes maintained?
In the first phase Oracle scans the segment from the back to find the position of the last row.
Afterwards it scan the segment from the beginning to find the position of the first free slot in a block in this segment. In case the two positions are the same, there is nothing to shrink. In case the two positions are different Oracle deletes teh row from the back and inserts it into the free position at front of the segement. Now Oracle scan teh segement from the back and front again and again until it finds that the two positions are the same.
Since it is DML statements performed to move the rows, the indexes are maintained at the same time. Only row level locks are used for these operations in the first pase of SHRINK TABLE statement.

The following restrictions apply to table shrinking:

1.) It is only possible in tablespaces with ASSM.
2.) You cannot shrink:
- UNDO segments
- temporary segments
- clustered tables
- tables with a colmn of datatype LONG
- LOB indexes
- IOT mapping tables and IOT overflow segments
- tables with MVIEWS with ON COMMIT
- tables with MVIEWS which are based on ROWIDs

The Oracle 10g Oracle comes with a Segment Advisor utility.
The Enterprise Manager, Database Control, even has a wizzard which can search for shrink candidates.

This advisor is run automatically by an autotask job on a regular basis in the default maintainance window.

You can use the built in package DBMS_SPACE to run the advisor manually as well…

(sysdba.wordpress.com)