Whenever there is sufficient memory, the standard Disk Sort may sort all the input data within its memory area, without writing to any of the work data sets that may have been provided. Sufficient memory, as discussed here, means that MFX’s memory area/address space is large enough to hold the MFX program, all of the input data, SORTIN or SORTOUT buffers (whichever are larger) and, if work data sets are allocated, SORTWKxx buffers.
The incore sort is not available to Disk Sorts taking checkpoints, using SUM, DUPKEYS, OUTREC, OUTFIL, an E14 or E16 exit routine, or producing VSAM output.