Adjusting performance automatically

Most users should set up the system to make performance adjustment automatically. When new systems are shipped, they are configured to adjust automatically.

The system can set performance values automatically to provide efficient use of system resources. You can set up the system to tune system performance automatically by:

• Adjusting storage pool sizes and activity levels

• Adjusting storage pool paging

Adjusting storage pool sizes and activity levels

Use the QPFRADJ system value to control automatic tuning of storage pools and activity levels. This value indicates whether the system should adjust values at system restart (IPL) or periodically after restart.

You can set up the system to adjust performance at IPL, dynamically, or both.

• To set up the system to tune only at system restart (IPL), select Configuration and Service > System Values > Performance in iSeries™ Navigator. Click the Memory Pools tab and select At system restart under Automatically adjust memory pools and activity levels. This is equivalent to setting the QPFRADJ system value to 1.

• To set up the system to make storage pool adjustments at system restart (IPL) and to make storage pool adjustments periodically after restart, select Configuration and Service > System Values > Performance in iSeries Navigator. Click the Memory Pools tab and select both At system restart and Periodically after restart under Automatically adjust memory pools and activity levels. This is equivalent to setting the QPFRADJ system value to 2.

• To set up the system to make storage pool adjustments periodically after restart and not at system restart (IPL), select Configuration and Service > System Values > Performance in iSeries Navigator. Click the Memory Pools tab and select Periodically after restart under Automatically adjust memory pools and activity levels. This is equivalent to setting the QPFRADJ system value to 3.

The storage pool values are not reset at system restart (IPL) to the initial values.

Adjusting storage pool paging

The dynamic tuning support provided by the system automatically adjusts pool sizes and activity levels for shared pools to improve the performance of the system. This tuning works by moving storage from storage pools that have minimal use to pools that would benefit from more storage. This tuning also sets activity levels to balance the number of threads in the pool with the storage allocated for the pool. To adjust the system, the tuner uses a guideline that is calculated based on the number of threads.

When dynamic adjustment is in effect, the following performance values are changed automatically to the appropriate settings:

• Machine (*MACHINE) memory pool size (QMCHPOOL system value)

• Base (*BASE) memory pool activity level (QBASACTLVL system value)

• Pool size and activity level for the shared pool *INTERACT

• Pool size and activity level for the shared pool *SPOOL

• Pool sizes and activity levels for the shared pools *SHRPOOL1-*SHRPOOL60

When dynamic adjustment is in effect (the QPFRADJ system value is set to 2 or 3), the job QPFRADJ that runs under profile QSYS is seen as active on the system.

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