Memory Pools

A memory pool is a logical division of main memory or storage that is reserved for processing a job or group of jobs. On your system, all main storage can be divided into logical allocations called memory pools. By default, the system manages the transfer of data and programs into memory pools. The memory pool from which user jobs get their memory is always the same pool that limits their activity level.

How data is handled in memory pools?

If data is already in main storage, it can be referred to independently of the memory pool it is in. However, if the needed data does not exist in any memory pool, it is brought into the same memory pool for the job that referred to it (this is known as a page fault). As data is transferred into a memory pool, other data is displaced and, if changed, is automatically recorded in auxiliary storage (this is called paging). The memory pool size should be large enough to keep data transfers (paging) at a reasonable level as the rate affects performance.

Type of Memory pools

• Private Memory Pools
• Shared Memory Pools
• Special Shared Pools (*MACHINE & *BASE)
• General Shared Pools (*INTERACT,*SPOOL,*SHRPOOL1-*SHRPOOL60)

Pool numbering schemes

Pools have two sets of numbering schemes: one is used within a subsystem and one is system-wide. The subsystem uses a set of numbers that refer to the pools it uses. Thus, when you create or change a subsystem description you can define one or more pools and label them 1, 2, 3, and so on. These are the designations of the subsystem pools, and they do not correspond to the pool numbers shown on the Work with System Status (WRKSYSSTS) display. A different set of numbers is used to keep track of all pools on the system. The Work with Subsystems (WRKSBS) display relates the subsystem pool identifiers and the column headings to the system pool identifiers.