General Information

Data sets are normally stacked according to statistics in the Control-M/Tape Stacking Database. This database is maintained by the stacking statistics utility CTTSTK that is usually run as part of the Control-M/Tape New Day procedure.

If no statistics have been gathered for a data set, a default number of megabytes is used to calculate how much space is needed to stack the data set. The default number of megabytes may be specified by either a DO STKDEFSZ statement in a Control-M/Tape rule, or by the STKDEFSZ installation parameter.

For more information about stacking statistics, see the description of the CTTSTK utility in the Control-M/Tape utilities chapter of the INCONTROL for z/OS Utilities Guide.

Logic for Determining Size of a Data Set to be Stacked

Control-M/Tape searches for a size for a data set to be stacked in the following locations. The first location that contains a value for size of the data set is used to stack the data set.

• a DO STKDEFSZ statement in a Control-M/Tape rule (if OVERRIDE STATISTICS is set to YES)
• the Stacking Database (called the Stacking Statistics file prior to version 5.1.4)
• a DO STKDEFSZ statement in a Control-M/Tape rule (if OVERRIDE STATISTICS is set to NO)
• Control-M/Tape installation parameter STKDEFSZ (in the CTTPARM parameter)

If no value is found in any of the above locations, the data set is not stacked.