The library containing cataloged procedures is a partitioned data set (PDS) or a partitioned data set extended (PDSE). The system procedure library is SYS1.PROCLIB. The installation can have many more procedure libraries with different names. You can also have procedures in a private library. The name of a cataloged procedure is its member name or alias in the library.

When a cataloged procedure is called, the calling step receives a copy of the procedure; therefore, a cataloged procedure can be used simultaneously by more than one job.

If you are modifying a cataloged procedure, do not run any jobs that use the procedure during modification.

In a JES3 system, you can specify UPDATE on the JES3 //*MAIN statement to update a procedure library.