Changing memory pool size

 

The size of a memory pool directly affects the amount of work that a subsystem can process. The more memory a subsystem has, the more work it can potentially complete. It is important that you monitor your system carefully before you start changing the parameters of your memory pools. You will also want to periodically recheck these levels, as some readjustment might need to be done.

Make sure you turn off the system tuner before you start manually changing memory pool sizes. The system tuner automatically adjusts the sizes of your shared memory pools to the amount of work the system is doing. If the system tuner is not turned off, the changes you make manually might be changed automatically by the tuner.

Turn the system tuner off by changing the Automatically adjust memory pools and activity levels (QPFRADJ) system value to 0. (0 = No adjustment)

 

Parent topic:

Managing memory pools

Related concepts
Pool numbering schemes

Related information
Manage iSeries performance Basic performance tuning Applications for performance management Experience report: The Performance Adjuster (QPFRADJ)

 

iSeries Navigator

1. In iSeries™ Navigator, expand My Connections > connection > Work Management > Memory Pools > Active Pools or Shared Pools.

2. Right-click the memory pool that you want to work in (for example, Interactive) and click Properties. The Memory Pool Properties window appears.

3. From the Configuration tab of the Properties window, you can change the defined amount of memory. Defined memory is the maximum amount of memory that the pool can use. The number you put here should reflect the amount of memory that you think the pool will need to support the subsystems it services.

The Base pool is the only memory pool that does not have a defined amount of memory. Instead it has a minimum amount of memory that it needs to run. The Base pool contains everything that is not allocated elsewhere. For example, you might have 1000 MB of memory on your system of which 250 MB is allocated to the Machine pool and 250 MB is allocated to the Interactive pool. 500 MB is not allocated to anything. This non-allocated memory is stored in the Base pool until it is needed.

Use caution when moving memory. Moving memory from one pool to another can fix one subsystem, but can cause problems for other subsystems, which in turn, can worsen system performance.

 

Character-based interface

Command: Change System Value (CHGSYSVAL )

Example: The following changes the size of the Machine pool.

CHGSYSVAL QMCHPOOL 'new-size-in-KB'

This corresponds to pool 1 on the WRKSYSTS display.

Example: The following changes the minimum size of the base pool.

CHGSYSVAL QBASPOOL 'new-minimum-size-in-KB'

This corresponds to pool 2 on the WRKSYSSTS display.

The QBASPOOL system value only controls the minimum size of the base pool. The Base pool contains all of the storage that is not allocated to other pools.

 

Change the size of a shared pool

Command: Change Shared Storage Pool (CHGSHRPOOL)

The changes to shared pools take effect immediately if the shared pool is active and sufficient storage is available.

Command: Work with Shared Storage Pools (WRKSHRPOOL)

This command gives you access to the names and status information of shared pools. By using the menu options you can change values for pool size and maximum activity levels.