Types of memory pools

On the your system, all main storage can be divided into logical allocations called memory pools. All memory pools in a system are either private or shared. There are private memory pools, shared memory pools, and special shared memory pools. As many as 64 memory pools, in any combination of private and shared pools, can be active at the same time.

Private memory pools

Private memory pools (also known as user-defined memory pools) contain a specific amount of main storage that can be used by a single subsystem to run jobs. These pools cannot be shared by multiple subsystems. They are identified in IBM® Navigator for i by the subsystem name. You can have as many as 62 private memory pools allocated for use in active subsystems.

Shared memory pools

Shared pools are either special or general; the Machine pool and Base pool are considered special shared pools, and all other shared pools are considered general shared pools. You can specify 63 of the 64 shared memory pools that are defined on the system for use when creating subsystem descriptions (the machine pool is reserved for system use).

Special Shared Pools (*MACHINE and *BASE)

*MACHINE
The Machine memory pool is used for highly-shared Machine and operating system programs. It is identified as Machine in IBM Navigator for i. The Machine memory pool provides storage for tasks the system must run that do not require your attention. The size for this memory pool is specified in the Machine memory pool size system value (QMCHPOOL). No user jobs run in this memory pool. (On the Work with System Status display (WRKSYSSTS), the Machine memory pool appears as system pool identifier 1.)
*BASE
The Base memory pool, identified as Base in IBM Navigator for i, contains all unassigned main storage on the system, (all main storage that is not required by another memory pool). The Base pool contains storage that can be shared by many subsystems. The Base memory pool is used for batch work and miscellaneous system functions. The Base memory pool minimum size (QBASPOOL) system value specifies the minimum size of the Base memory pool. The activity level for this memory pool is specified in the Base memory pool maximum eligible threads (QBASACTLVL) system value. (On the Work with System Status display (WRKSYSSTS), the Base memory pool appears as system pool identifier 2.)

General Shared Pools

General shared pools are pools of main storage that multiple subsystems can use at the same time. On the character-based interface, they are identified as follows:
  • *INTERACT is the interactive storage pool used for interactive jobs.
  • *SPOOL is the storage pool used for spool writers.
  • *SHRPOOL1 through *SHRPOOL60 are storage pools that you can use for your own use.

In IBM Navigator for i, the general shared pools are identified as Interactive, Spool, and Shared 1 - Shared 60.