ALTERMOD is designed as a one-time update operation against load modules from old systems. You can use IEBCOPY to update partitioned data set load modules that were written by a linkage editor prior to MVS/370, so that they will load faster. Load modules processed with the linkage editor in MVS/370 and subsequent versions of MVS and DFSMS do not require alterations, nor do program objects in a PDSE.

ALTERMOD will place correct relocation dictionary (RLD) counts and segment block counts into control records inside the module. ALTERMOD performs this update without making a new copy of the load module. It can be used to alter modules that might have erroneous RLD counts. Examples of modules that might have erroneous RLD counts are modules that were created by a program other than the linkage editor or copied by a program other than IEBCOPY.

When you use a SELECT statement to identify members to be processed by ALTERMOD, you cannot rename them.