Some APPC/MVS calls have a version number as the last character of the call name (for example, ATBIDN1). That number corresponds to the version of APPC/MVS in which the call was introduced.

To determine which calls are valid on a system, you can obtain the current APPC/MVS version number from the APPC/MVS Version service. On any system, valid APPC/MVS calls include those with no version number in the call name or a version number less than or equal to the current APPC/MVS version number. For example, calls to ATBIDEN and ATBIDN1 are both valid when the current APPC/MVS version number is 1 or higher. Likewise, a call named ATBxxx2 would be valid only when the current APPC/MVS version number is 2 or higher.

For more information about APPC/MVS version numbers, including how to obtain the version number that is current on your system, see the Version service in z/OS MVS Programming: Writing Transaction Programs for APPC/MVS.