Relationship of the Exec Interpreters

The REXX/VM, EXEC 2, and CMS EXEC interpreters have their own distinct keywords and syntax. So for example, you cannot place EXEC 2 statements within a REXX program.

The three interpreters coexist, so exec programs will continue to correctly process with no user modifications, regardless of the language. To run CMS EXEC programs as EXEC 2 programs, you must convert the exec programs to EXEC 2 programs.

While you may not use, for example, EXEC 2 language statements in an exec to be interpreted by the REXX/VM interpreter, nor REXX language statements in an exec to be interpreted by the EXEC 2 interpreter, any exec can call another exec, regardless of the language. Thus an EXEC 2 procedure may be run from within a CMS EXEC procedure, and vice versa.

To allow greater user flexibility with EXEC 2 and the Procedures Language REXX/VM Interpreter, automatic cleanup of an active OS or VSAM environment is not performed at command completion, as it is in the CMS EXEC processor. It is your responsibility to ensure that OS and VSAM cleanup functions are performed when needed. You can accomplish this by using the EXECOS command. For more information on the EXECOS command, see z/VM: CMS Commands and Utilities Reference.

The CMS EXEC processor invokes OS and VSAM cleanup after the execution of any CMS command. Consequently, any CMS EXEC used resets the OS and VSAM environments if it contains a CMS command that is processed.