AIX Tips
Adjusting the AIX kernel parameters:
Unlike many other UNIX operating systems, AIX does not provide the ability to directly configure most kernel parameters. Instead, the AIX kernel dynamically allocates and reallocates resources as they are needed (up to a predefined limit).
For calendar server installations, the only kernel parameter that should be altered is maxuproc (maximum number of processes per user-ID), which can be modified via SMIT (AIX's menu-based system administration utility) or the command line utility chdev.
To see a complete list of the parameters and their current values, run the lsattr command:
% /etc/lsattr -E -l sys0
To see the current values assigned to a particular kernel parameter, use the lsattr command with the parameter name. For example:
% /etc/lsattr -E -l sys0 -a maxuproc
To change the value of the maxuproc parameter, use the chdev command. For example:
% /etc/chdev -l sys0 -a maxuproc = 200
As stated above, the AIX kernel dynamically allocates and reallocates resources as they are needed up to a predefined limit. The known limits of the parameters are as follows:
Table C 8 • AIX kernel parameters
Kernel Parameter Description Upper Limit
soft file limit per process 2000
hard file limit per process 2000
max. number of concurrent processes per user-id: configurable, cannot exceed 131,072
max. number of concurrent processes on the system 131,072
max. number of open files 200000
max. number of message queue identifiers 4096
max. number of message headers unlimited; 8192 per message queue.
max. number of semaphore identifiers 4096
max. number of semaphores unlimited; 65535 per semaphore id.
The practical limits of the server, defined as the maximum number of concurrent users on a system, are effectively determined by the upper limits of the maximum number of open files. Assuming there are no other activity or resource requirements on the system, the maximum number of concurrent users (lck_users) under AIX is approximately 10000*20+60=200060.
At least as of version 5.1, it should not be necessary to do any special configuration for such parameters as SHMMAX, as it appears this is configured to allow all memory to be used as shared memory. That is the sort of configuration commonly used for other databases such as DB/2.
It may, however, be necessary to modify the global ulimit information in /etc/security/limits, as the default hard limits for file sizes (fsize) and numbers of files (nofiles) may be too low.
(ii) Reset an Unknown Root Password:
The following procedure describes how to recover access to root privileges when the system's root password is unavailable or unknown. The following procedure requires some system downtime. If possible, schedule your downtime when it least impacts your workload to protect yourself from a possible loss of data or functionality.
1. Insert the product media for the same version and level as the current installation into the appropriate drive.
2. Power on the machine.
3. When the screen of icons appears, or when you hear a double beep, press the F1 key repeatedly until the System Management Services menu appears.
4. Select Multiboot.
5. Select Install From.
6. Select the device that holds the product media and then select Install.
7. Select the AIX version icon.
8. Define your current system as the system console by pressing the F1 key and then press Enter.
9. Select the number of your preferred language and press Enter.
10. Choose Start Maintenance Mode for System Recovery by typing 3 and press Enter.
11. Select Access a Root Volume Group. A message displays explaining that you will not be able to return to the Installation menus without rebooting if you change the root volume group at this point.
12. Type 0 and press Enter.
13. Type the number of the appropriate volume group from the list and press Enter.
14. Select Access this Volume Group and start a shell by typing 1 and press Enter.
15. At the # (number sign) prompt, type the passwd command at the command line prompt to reset the root password. For example:
16. # passwd
17. Changing password for "root"
18. root's New password:
Enter the new password again:
19. To write everything from the buffer to the hard disk and reboot the system, type the following:
sync;sync;sync;reboot
When the login screen appears, the password you set in step 15 should now permit access to root privileges.
(iii) Steps for breaking the mirror and replacing the failed HDD:
unmirrorvg workvg hdisk7
reducevg workvg hdisk7
rmdev -l hdisk7 -d
chpv –c--- if the VG is rootvg to clear boot record before unmirroing
Replace the failed disk drive with a new one, and name it hdisk7 by executing
the following commands:
extendvg workvg hdisk7
mirrorvg workvg
Rootvg mirroring:
When the rootvg mirroring performed:
1. Run the bosboot
The bosboot command
Access Memory)
required to customize
2. Run the bootlist
The bosboot command
does not update
access memory).
To Migrate Particular logical volume to some other location :
migratepv -l loglv00 hdisk1 hdisk0
Command to sync the ODM :
synclvodm -v rootvg
Unlike many other UNIX operating systems, AIX does not provide the ability to directly configure most kernel parameters. Instead, the AIX kernel dynamically allocates and reallocates resources as they are needed (up to a predefined limit).
For calendar server installations, the only kernel parameter that should be altered is maxuproc (maximum number of processes per user-ID), which can be modified via SMIT (AIX's menu-based system administration utility) or the command line utility chdev.
To see a complete list of the parameters and their current values, run the lsattr command:
% /etc/lsattr -E -l sys0
To see the current values assigned to a particular kernel parameter, use the lsattr command with the parameter name. For example:
% /etc/lsattr -E -l sys0 -a maxuproc
To change the value of the maxuproc parameter, use the chdev command. For example:
% /etc/chdev -l sys0 -a maxuproc = 200
As stated above, the AIX kernel dynamically allocates and reallocates resources as they are needed up to a predefined limit. The known limits of the parameters are as follows:
Table C 8 • AIX kernel parameters
Kernel Parameter Description Upper Limit
soft file limit per process 2000
hard file limit per process 2000
max. number of concurrent processes per user-id: configurable, cannot exceed 131,072
max. number of concurrent processes on the system 131,072
max. number of open files 200000
max. number of message queue identifiers 4096
max. number of message headers unlimited; 8192 per message queue.
max. number of semaphore identifiers 4096
max. number of semaphores unlimited; 65535 per semaphore id.
The practical limits of the server, defined as the maximum number of concurrent users on a system, are effectively determined by the upper limits of the maximum number of open files. Assuming there are no other activity or resource requirements on the system, the maximum number of concurrent users (lck_users) under AIX is approximately 10000*20+60=200060.
At least as of version 5.1, it should not be necessary to do any special configuration for such parameters as SHMMAX, as it appears this is configured to allow all memory to be used as shared memory. That is the sort of configuration commonly used for other databases such as DB/2.
It may, however, be necessary to modify the global ulimit information in /etc/security/limits, as the default hard limits for file sizes (fsize) and numbers of files (nofiles) may be too low.
(ii) Reset an Unknown Root Password:
The following procedure describes how to recover access to root privileges when the system's root password is unavailable or unknown. The following procedure requires some system downtime. If possible, schedule your downtime when it least impacts your workload to protect yourself from a possible loss of data or functionality.
1. Insert the product media for the same version and level as the current installation into the appropriate drive.
2. Power on the machine.
3. When the screen of icons appears, or when you hear a double beep, press the F1 key repeatedly until the System Management Services menu appears.
4. Select Multiboot.
5. Select Install From.
6. Select the device that holds the product media and then select Install.
7. Select the AIX version icon.
8. Define your current system as the system console by pressing the F1 key and then press Enter.
9. Select the number of your preferred language and press Enter.
10. Choose Start Maintenance Mode for System Recovery by typing 3 and press Enter.
11. Select Access a Root Volume Group. A message displays explaining that you will not be able to return to the Installation menus without rebooting if you change the root volume group at this point.
12. Type 0 and press Enter.
13. Type the number of the appropriate volume group from the list and press Enter.
14. Select Access this Volume Group and start a shell by typing 1 and press Enter.
15. At the # (number sign) prompt, type the passwd command at the command line prompt to reset the root password. For example:
16. # passwd
17. Changing password for "root"
18. root's New password:
Enter the new password again:
19. To write everything from the buffer to the hard disk and reboot the system, type the following:
sync;sync;sync;reboot
When the login screen appears, the password you set in step 15 should now permit access to root privileges.
(iii) Steps for breaking the mirror and replacing the failed HDD:
unmirrorvg workvg hdisk7
reducevg workvg hdisk7
rmdev -l hdisk7 -d
chpv –c
Replace the failed disk drive with a new one, and name it hdisk7 by executing
the following commands:
extendvg workvg hdisk7
mirrorvg workvg
Rootvg mirroring:
When the rootvg mirroring performed:
1. Run the bosboot
The bosboot command
Access Memory)
required to customize
2. Run the bootlist
The bosboot command
does not update
access memory).
To Migrate Particular logical volume to some other location :
migratepv -l loglv00 hdisk1 hdisk0
Command to sync the ODM :
synclvodm -v rootvg
