Identifies the module and CSECT to be disassembled. Must be the first control statement in the input stream, and specifies the module name, CSECT name, and optionally CLASS name for program objects.

z/OS

z/OS needs the module name. If you specify the name of a PDS or PDSE in the SYSLIB DD statement, then the module name you specify in the Module-CSECT statement identifies a load module or a program object to be disassembled, which must be a member of that PDS or PDSE. Otherwise, the name is ignored (but still needed); the PDS or PDSE member or sequential data set identified by the SYSLIB DD statement is assumed to be an object module. The CSECT name is optional. If it is specified, the named CSECT must exist in the module or object module. If omitted, the CSECT with ESDID=0001 is disassembled.

z/VM

On CMS, you must provide a module name but it is not used for object decks. For object decks, only the first CSECT is disassembled; selection of specific CSECTs is not possible. For CMS modules, the CSECT name is optional. If it is specified, the named CSECT must exist in the module.

z/VSE

On z/VSE, a phase does not contain any information allowing selection of individual CSECTs. The phase is therefore viewed as one CSECT where the CSECT name is determined by the CSECT name on this statement, if present; otherwise it is the module name.