The SORTOUnn DD statements allocate the tape units used as input to the merge phase. They are required unless the DYNATAPE option (available only under z/OS) is used.
Although it is not necessary to specify the SORTOUnn DD statements when DYNATAPE is used, it is a good idea to pre-allocate at least two SORTOUnn data sets when the DYNATAPE option is specified. This ensures that the minimum required number of tape units will be available for the merge phase. When additional units are available, DYNATAPE will provide performance benefits.
The following rules should be observed in coding the SORTOUnn DD statements:
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At least two tape units must be allocated in the absence of DYNATAPE. However, allocating more units will make the merge phase complete more quickly.
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Each statement must be allocated to a unique tape drive. If DYNATAPE is in effect, the tape unit name must be the same as the unit name specified in the TAPENAME PARM.
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All the tape units must operate at the same recording density. For best performance, multiple density units should be run at the highest density.
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For each SORTOUnn statement, replace the 'nn' with a two digit number between 01 and 99. The numbers need not be consecutive.
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Specify DISP=(NEW,KEEP), a permanent DSNAME and VOL=PRIVATE so that a scratch tape is used and the tape volumes are unloaded.
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Specify the DEFER option in the UNIT parameter so that mount messages to the operator that do not pertain to MAXSORT are suppressed.