Space switch or non-space switch

You can define a PC routine as either a space switch routine or a non-space switch routine. When making this decision, consider the nature of the PC routine and the data it manipulates.

Use a non-space switch PC routine if the PC routine must support problem state callers and must run in supervisor state in the caller's address space. If you do not have these requirements, you can use a space switch routine, which has certain advantages. A space switch routine:

Provides code isolation
Allows you to access data in multiple address spaces
Prevents you from having to place your code in common storage.

To define a PC routine as either a space switch or non-space switch routine, specify the SSWITCH parameter on the ETDEF macro. The default is to define the routine as a non-space switch routine.