To make a program available to all system users, copy it to a member of a system library. The system library can be one that is defined in the linklist concatenation, such as SYS1.LINKLIB, or it can be SYS1.LPALIB, which is allocated at IPL and therefore always available.

Programs in system libraries should be (and programs in SYS1.LPALIB must be) reentrant--that is, they must use dynamic storage to allow multiple and concurrent executions of the program. The sample programs in this document are reentrant, and macro descriptions in Macro Syntax and Parameters indicate steps to take to make a program reentrant.