Tuning Disk Space Allocations
With the operational feature RELEASE turned ON (this is the delivered default), MFX automatically supplements and releases any disk space you have allocated for intermediate storage, making the allocation of the correct amount of SORTWK space an automatic, sort-controlled process. For general sorting purposes, you don’t need to be concerned with precise SORTWK space allocations. However, allocating SORTWK space in cylinders, rather than blocks or tracks, will usually yield optimal performance.
For best performance with file sizes greater than 30 megabytes, especially when DYNALLOC is not enabled, allocate the required space across 4 to 6 SORTWK devices.
Message WER124I is provided in some applications in order to permit those who are interested in a finely-tuned sort execution to improve intermediate storage allocation for future runs. Routinely overallocating SORTWK, relying on RELEASE=ON, will delay sort step execution until all the space requested (including the excess space) is available, and will waste this excess space until its released at the end of Phase 1. Routinely underallocating by a large amount assumes that the needed storage will always be physically available. If, for some reason, the required storage cannot be obtained on any volume assigned for sort work areas, MFX will terminate with a SORT CAPACITY EXCEEDED error.
A sort is considered to finely tuned when WER124I reports an overallocation factor between 1.00 and 1.50.