Enabling Job Restart Functionality

The restart functionality is governed by two environment variables:

ES_JES_RESTART

Setting this variable to Y has the following effects:

ESMAC will display new fields for a job's details on the Output Hold queue, along with a Restart button. The new fields allow you to specify the step and procstep at which the job is to restart.
When the job is run, the lexical files (MFELX*.DAT) associated with the job will no longer be cleaned up when the job is completed; instead, these files will be cleaned up when the job is deleted.

MF_UCC11

Note: This environment variable works independently of the JCL RESTART parameter.

JCL job restart functionality is disabled by default. It can be enabled, with varying behaviors, using one of the following values:

When set to Y, restarting a job with DISP=(NEW,CATLG) data sets will not result in job failure caused by the data set already being cataloged.
When set to YA, running a job with DISP=(NEW,CATLG) data sets will not result in job failure caused by the data set already being cataloged.
When set to M, MA or MR, when restarting a job, cataloged data sets are presumed to have an initial disposition of MOD, rather than NEW . As a result, any new data is appended to the existing data set.
When set to N, MF_UCC11 is not set so a data set with an initial disposition of NEW may cause an error when restarting the job if the data set already exists. The setting of the MF_UCC11 value can be made on a job-by-job basis using either the JCL user exit, MFJUXIT, or the Advanced Restart Functionality.

Additionally, when set to Y or YA, if the job uses GDG data sets, the GDG generation is reset to the level used in the previous job, ensuring that the restart will automatically pick up the correct GDG generation.

When restarting a job with any of the above values set, COND Code Processing and IF/THEN logic that is dependent upon COND codes from prior steps that are skipped by the RESTART, will work as expected with no changes to the JCL.