Often there is more than one version of a macro, differentiated by additional keywords or new or expanded function. For example, version 1 of the IXLCONN macro provides several new keywords in support of the structure alter function, while version 3 of the IXLCONN macro provides a new keyword to support a new resource name length attribute of a lock structure.

You can request a specific version of a macro based on the needs of your application, but you should also be attuned to the storage constraints of the installation. The version of a macro might affect the length of the parameter list generated when the macro is assembled. The size of the parameter list might grow from release to release of z/OS, perhaps affecting the amount of storage your program needs.