System storage requirements

One factor that might influence your decision to use subspaces is the amount of virtual and central storage that the system requires to manage them. This storage overhead can affect system performance.

The system allocates storage for its own use from subpool 255 when a program:

Makes storage eligible to be assigned to a subspace
Creates a subspace
Assigns more than 2 segments of storage below 16 megabytes to a subspace.

The system deallocates its storage when the program deletes the subspace or makes the storage ineligible to be assigned to a subspace.

The amount of storage that the system requires for its own use depends on whether the subspace storage is above or below 16 megabytes. The system requires more storage to manage subspaces below 16 megabytes.

Use the following guidelines to plan for the system's storage requirements:

Table 1. System storage requirements when managing subspaces
The System Uses:	For Each:
8192 bytes	Address space in which a program issues IARSUBSP IDENTIFY
1024 bytes	Segment below 16 megabytes specified on IARSUBSP IDENTIFY
10376 bytes	Subspace created
1024 bytes	Segment below 16 megabytes specified on IARSUBSP ASSIGN, after the first two such segments