RECOMMENDATIONS SECTION

All recommendations contained in this report are based on the conditions which were present when the performance data was collected. It is possible that conditions which were not present at that time may cause some of these recommendations to result in worse performance. To minimize this risk, analyze data from several different days, implement only regularly occurring recommendations, and implement them one at a time or as groups of related parameters.

Additional memory may improve performance. If possible, borrow some memory for test purposes, and monitor system performance and resource utilization before and after its installation.

NOTE: The following 4 vmo changes should be made all at once. These changes are based on new information presented at the 2006 IBM System p Technical University and an article in the Aug/Sept 2006 issue of IBM Systems Magazine, Open Systems edition.

Change the value of the lru_poll_interval parameter from 0 to 10 with the command 'vmo -o lru_poll_interval=10'. The -o flag changes the value of a parameter only until the next reboot. To make the change permanent, use the command 'vmo -p -o lru_poll_interval=10'. The lru_poll_interval parameter is used to make the page stealing daemon more responsive.

Change the value of the maxperm% parameter from 45 to 80 with the command 'vmo -o maxperm%=80'. The -o flag changes the value of a parameter only until the next reboot. To make the change permanent, use the command 'vmo -p -o maxperm%=80'.

Change the value of the maxclient% parameter from 45 to 80 with the command 'vmo -o maxclient%=80'. The -o flag changes the value of a parameter only until the next reboot. To make the change permanent, use the command 'vmo -p -o maxclient%=80'.

Change the value of the minperm% parameter from 15 to 5 with the command 'vmo -o minperm%=5'. The -o flag changes the value of a parameter only until the next reboot. To make the change permanent, use the command 'vmo -p -o minperm%=5'.

This is the end of this set of vmo parameter changes that should be implemented together.

Change the value of maxfree from 1240 to 2400 with the command 'vmo -o maxfree=2400'. The -o flag changes the value of a parameter only until the next reboot. To make the change permanent, use the command 'vmo -p -o maxfree=2400'. This change is recommended based on formulas discussed at IBM's pSeries Technical University. The recommended value for minfree is 1200 and the value for maxpgahead was 16. The j2_maxPageReadAhead value used was 128. The value of lcpu reported by sar was 5.0. The number of memory pools seen was 2. The magnitude of this change has been limited to prevent the recommendation of very large changes. Changing this parameter in smaller increments is a much safer way to tune the system.

Change the value of minfree from 600 to 1200 with the command 'vmo -o minfree=1200'. The -o flag changes the value of a parameter only until the next reboot. To make the change permanent, use the command 'vmo -p -o minfree=1200'. This change is recommended based on formulas discussed at IBM's pSeries Technical University. The following data was used in this calculation: The number of memory pools seen was 2. The value of lcpu reported by sar was 5.0. The number of active CPUs reported by sysconf is 1.

Change the scheduler's ratio of CPU penalty to recent CPU usage (the R value) from 16 to 5 with the command 'schedo -o sched_R=5'. The -o flag changes the value of a parameter only until the next reboot. To make the change permanent, use the command 'schedo -p -o sched_R=5'. This change should help the scheduler distinguish between background processes and those running as interactive foreground processes.

Fix the problems seen in the layout of the system's paging spaces. Exact recommendations require information about future plans, such as any physical volumes which may be added shortly or anticipated changes to system load and storage requirements. Here is the problem seen by this program:

• The total size of the paging spaces is smaller than the amount of physical memory.