SCLM temporary data set allocations

Many installations specify one or more I/O unit names as Virtual Input Output (VIO) devices at system generation time. Use of these devices typically improves system performance by eliminating much of the overhead and time required to move data physically between main storage and an I/O device.

To take advantage of this facility, specify the name of the VIO unit in your project definition as the VIOUNIT parameter on the FLMCNTRL macro. This unit will be used for all temporary data sets under the following conditions:

IOTYPE = O, P, S, or W
CATLG = N
RECNUM <= the MAXVIO parameter.

Some of the temporary data sets used by versioning will use the VIO unit as well as long as the size of the temporary data set to be allocated is less than or equal to the MAXVIO value.

Temporary data set allocations that fail to meet any of the preceding conditions will be allocated using the unit specified via the DASDUNIT parameter on the FLMCNTRL macro.

The default value for MAXVIO is 5000, and the maximum allowable value is 2147483647. A relatively large value should be specified in order to ensure that SCLM temporary data sets are allocated using the VIO unit. If SCLM functions fail for lack of memory (S80A ABEND or S878 ABENDs), try reducing this value.

The size of the temporary data sets allocated for translators is determined by the attributes specified on the FLMALLOC macros in the language definition. The size of the temporary data sets used by versioning is based on the attributes of the source data set being versioned.