The control file is normally a very small disk file whose size is based on the maximum number of strings that can be produced for the sort operation currently being executed.

Control file records are 3 words in length, and blocks are 90 words in length. The maximum number of control file rows is 64, and the number of physical blocks per row is 4—unless the amount of disk space provided is extremely large. The last two rows of the control file contain restart information when restartable sorts are requested. When a restartable sort is desired, file equation should be used to give a unique title to the control file. For example:

<i> FILE DISKC (TITLE=JOBNAME/SORTCONTROL)

Other attributes in the file equation for the control file can be modified, but the probability of failure is high if attributes such as AREAS, AREASIZE, MAXRECSIZE, and BLOCKSIZE are modified by file equation.