Every PL/I program requires run-time library routines to execute.
Do not make more than one PL/I run-time library available to your applications at execution time. For example, there should be one and only one PL/I run-time library, such as SCEERUN for Language Environment, in LNKLST. If you have more than one you will either get hard-to-find errors or you will have an unused load library in your concatenation. In addition, if you have more than one run-time library in your concatenation, then you have an invalid configuration that is not supported by IBM.
If you have not already moved to Language Environment and are using a pre-Language Environment PL/I compiler, such as OS PL/I V2R3, you will need to read Planning the move to Language Environment.
If you have already moved to Language Environment and are migrating to the new IBM Enterprise PL/I for z/OS compiler, you can begin reading about compiler migration in Planning to move to the new compiler.