Summary -

In this topic, we described about the Altering Load Modules with detailed example.

ALTERMOD is designed as a one-time update operation against load modules from old systems. IEBCOPY to update PDS load modules written prior to MVS/370, so that they will load faster.

ALTERMOD will place correct relocation dictionary counts and segment block counts into control records inside the module.

ALTERMOD performs the above update without making a new copy of the load module. The ALTERMOD statement ignored under these conditions:

  • The load modules are link edited with the noneditable (NE) attribute.
  • The data set is a PDSE.
Note! When SELECT statement used to identify members to be processed by ALTERMOD can’t be renamed.


All members of data set dataset1.lib, members A, B, and C of data set are altered in place.

  //Dataset1DD  DSNAME=dataset1.lib,DISP=(OLD,KEEP)
  //SYSIN    DD  *
       SELECT    MEMBER=(A,B)

Let’s discuss the example in detail.

  • Dataset1 DD defines the partitioned data set dataset1.lib, which has been previously created and cataloged.
  • SYSIN DD defines the control data set, which follows in the input stream.
  • The ALTERMOD statement plus the following SELECT statement indicates that members A and B are to be altered in place.
  • The remainder of dataset1.lib is unchanged.