Data set cleanup and Prevent-NCT2 processing

Before executing a restart job, catalog and VTOC maintenance are often required in order to prevent file-related errors during the processing of the restarted job.

When a job tries to create a data set that already exists or that has a name that is already cataloged, the job may fail with a DUPLICATE DATASET ON VOLUME error, or a NOT CATLGD 2 error. As a result, the production workflow continues using an incorrect version of the data set. In either case, the impact on the production workflow can be severe. This problem is especially likely in non-restart reruns. Therefore, data set cleanup is necessary.

The data set cleanup process automatically performs all required catalog adjustment. It accesses the SYSDATA of previous runs of the job order to analyze file creation and deletion and catalog information. Since a job may fail multiple times, analysis of the SYSDATA begins with the archived SYSDATA of the most recent non-restarted run.

As part of data set cleanup, Control-M/Restart

• deletes and uncatalogs the old data sets
  This prevents DUPLICATE DATSET ON VOLUME and NOT CATLGD 2 errors.
• performs Generation Data Set (GDG) Adjustment (described below)

The user can, however, exclude files from data set cleanup if desired, in either of the following ways:

• by specifying the names of the data sets to be excluded in appropriate control statements that are placed in a user-defined library member
  For more information, see EXCLUDE DSN parameter.
• by specifying the DD name in the appropriate parameter member
  For more information, see Format of the $EXCLUDE member.

Control-M/Restart automatically performs data set cleanup prior to any restart.

Data set cleanup can also be performed even prior to the original run of a job. This can be important because data sets accessed by the job can have DUPLICATE DATA SET or NOT CATLGD 2 errors that were generated by an entirely different job. As mentioned earlier in this chapter

• when data set cleanup is performed as part of the original job request, it is called Prevent-NCT2 processing
• otherwise (that is, when performed independently of the original job request), the term "data set cleanup" is used

For details, see Data set cleanup prior to the original run.