Often there is more than one version of a macro, differentiated by additional parameters or new or expanded function. For example, version 1 of the IXGCONN macro provides a connection to a log stream, while version 2 adds new parameters in support of resource manager programs. This is different than using the SPLEVEL macro to select a macro version level to solve problems of downward compatibility.

You can request a specific version of a macro based on the parameters you need to use in your application, but you should also be attuned to the storage constraints of the program. The version of a macro might affect the length of the parameter list generated when the macro is assembled, because when you add new parameters to a macro, the parameter list must be large enough to fit them. The size of the parameter list might grow from release to release of z/OS®, perhaps affecting the amount of storage your program needs.