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System dump in AIX



If a kernel panic occures, a dump will be invoked automatically in AIX. The followings are dumped during the dump process.
  1. List of currently running processes and related information about the process
  2. Curretnly mounted filesystems, inode table and open file table
  3. currently configured ttys and their status
  4. Memory buffers for data
  5. system buffers
  6. system variables and statistics
  7. Kernel's own record of process it is currently running.




Configuring dump devices in AIX

sysdumpdev command is used to

change the primary or secondary dump device designation in a running system in AIX.

 sysdumpdev 
           -l list the current dump destination
           -L view satistical information about previus dump
           -e estimate the dump size
           -d  directory to copy the dump during boot time
           -p   to set the device as primary dump device
           -s  to set the device as secondary dump device
           -P to make the changes permanent even after reboot

Examples:

To permanently make /dev/hd7 as the primary dump device
 # sysdumpdev -Pp /dev/hd7

To make /dev/sysdumpnull as the secondary dump device
 # sysdumpdev -s /dev/sysdumpnull

To estimate the dump size
 #sysdumpdev -e




To Start the dump manually in AIX

sysdumpstart command is used to start a kernel dump to the primary or secondary dump device. When the dump completes, the system halts. Use the kdb command to examine the dump.
 
# sysdumpstart {-p | -s}




Copying system dump in AIX
  • If there is enough space to copy the dump to /var/adm/ras directory, then it will be copied directly during reboot. 
  • Dump is copied as /var/adm/ras/vmcore.x file. 
  • If there is not enough space, then "copydumpmenu" is run by /sbin/rc.boot to display the copy dump menu. Using this copydumpmenu utility, a dump can be copied to removable such as tape.


snap utility can be used to gather system information along with dump and compress the information in a tar file.

snap
    -a  gathers all system configuration information
    -c  creates compressed pax image (snap.pax.Z)
    -e  HACMP specifig information
    -g  gathers general info
    -f  gathers filesystem info
    -k  gathers kernel info
    -d  optional snap commnad output directory
       default directory is /tmp/ibmsupt
    -D  gathers dump and /unix
    -o   cpoies the compressed image to tape or diskette

Example:
To send dump with other gathered information in to tape drive
 # snap -gfkD -o /dev/rmt0




Analyzing system dump


kdb command is an interactive utility for examining an OS image or the running kernel.
 
  kdb KernelFile]]




LED Codes Related to dump


 0c0 - Dump completed successfully
 0c2 - Dump started
 0c4 - Dump unsuccesful. Not enough space on dump device
 0c5 - Dump failed to start
 0c9 - System initiated dump started


Labels: AIX

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I'm Parthiban, An UNIX System Admin by Profession. I'm Experienced in Linux/Unix System Administration and Scripting. I have done lot of work on the infrastructure Mgmt side in Linux, UNIX and Windows system administration, Hardware, Storage and Data center. I'm blogging since 2008.
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2 Comments for "System dump in AIX"

Hello Parthiban;
I am traying to know much more about how to get the root cause of the system crash by analyzing the dump with kdb.
On my case when you use stat inside "kdb" I do not get the ref code as expected. Do you have any example to post here how to analyze aix dump ?

Hello Parthiban.....

How to take the backups of SYSdump and Device?

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