The MODS statement identifies the exits to be taken and indicates the name of the separately compiled, user-written routine to take control at that point. The same routine (e.g., deleting selected records) could take effect in different phases, but cannot be loaded more than once in a single phase.
Note that merge and copy are executed entirely in Phase 3 and are therefore restricted in the exits which they can use. A merge application cannot use exits E11 through E27. A copy application can use exit E15 but not exits E32 or E61.
Assemble each routine as a separate program and place it in a partitioned data set or in the SYSIN input stream; MFX copies the SYSIN routines to the SORTMODS library for linkage editing. (If a SYSIN module is to be used at more than one exit point, each exit must have its own compiled copy of the module in SYSIN.) If MFX linkage edits an exit routine, the module must have an entry point whose name is that of the MFX exit; for example, in order to function as an E35 routine, MYEXIT must include an entry point or CSECT labeled E35.
If a routine has already been link-edited, this can be indicated in the MODS statement. When all the exits in a particular phase need to communicate with one another, the MODS statement can be used to instruct the sort to link-edit them together.