Making dynamic calls

In these forms of the CALL statement, the called COBOL subprogram is not link-edited with the main program. Instead, it is link-edited into a separate program object, and is loaded at run time only when it is required (that is, when called). The program-name in the PROGRAM-ID paragraph or ENTRY statement must be identical to the corresponding program object name or program object alias of the program object that contains the program. One of the common reasons for messages CEE3593I, CEE3541S, CEE3574I, and IGZ0178S during dynamic calls is that the program-name in the PROGRAM-ID paragraph is not identical to the corresponding program object name or alias.

Each subprogram that you call with a dynamic CALL statement can be part of a different program object that is a member of either the system link library or a private library that you supply. In either case it must be in an MVS load library; it cannot reside in the z/OS® UNIX file system. When a dynamic CALL statement calls a subprogram that is not resident in storage, the subprogram is loaded from secondary storage into the region or partition that contains the main program, and a branch to the subprogram is performed.

The first dynamic call to a subprogram within a run unit obtains a fresh copy of the subprogram. Subsequent calls to the same subprogram (by either the original caller or any other subprogram within the same run unit) result in a branch to the same copy of the subprogram in its last-used state, provided the subprogram does not possess the INITIAL attribute. Therefore, the reinitialization of either of the following items is your responsibility:

• GO TO statements that have been altered
• Data items

If you call the same COBOL program in different run units, a separate copy of WORKING-STORAGE is allocated for each run unit.

Restrictions: You cannot make dynamic calls to:

• COBOL DLL programs
• COBOL programs compiled with the PGMNAME(LONGMIXED) option, unless the program-name is less than or equal to eight characters in length and is all uppercase
• COBOL programs compiled with the PGMNAME(LONGUPPER) option, unless the program-name is less than or equal to eight characters in length
• More than one entry point in the same COBOL program (unless an intervening CANCEL statement was executed)

Examples: static and dynamic CALL statements