The DFSMS level determination call (IGWASYS) returns the version, release and modification levels of DFSMS. It also returns a code number to represent the name of the product that contains DFSMS. These four numbers represent the environment that DFSMS was designed to run in. That level might be earlier than the release for the rest of the operating system.

An alternative technique to determine the level of the system is described in Determining Level and Name of DFSMS.