Use memory object sorting

Memory object sorting uses a memory object in 64-bit virtual storage to improve the performance of sort applications that use DFSORT's Blockset Technique. A memory object is a data area in virtual storage that is allocated above the bar and backed by central storage. With memory object sorting, a memory object is used in place of and along with disk for temporary storage of records during a sort. Memory object sorting reduces I/O processing, which in turn reduces elapsed time, EXCPs, and channel usage. Memory object sorting is recommended for large input data sets when a sufficient amount of central storage is available.

You can control the maximum size of a memory object for a memory object sorting application with the MOSIZE parameter. MOSIZE can direct DFSORT to dynamically determine the maximum size of a memory object, subject to the available central storage at the start of the run. MOSIZE=0 means that DFSORT will not use memory object sorting.

The actual size of a memory object that a memory object sorting application uses depends upon several factors. See the MOSIZE description in OPTION control statement for more details.

The following are actions you can take that might increase the use of memory object sorting:

Verify that a sufficient size for memory objects is defined by the MEMLIMIT parameter on the JOB or EXEC JCL statement.
Specify MOSIZE=MAX.
Specify generous extent sizes for work data sets, especially for secondary extents.
Verify that IEFUSI does not place any restrictions on the size of the memory objects a single address space can create.
Ensure that DFSORT has accurate information about the input file size. DFSORT can automatically estimate the file size for disk input data sets and tape data sets managed by DFSMSrmm or a tape management system that uses ICETPEX. See File size and dynamic allocation for information on situations where DFSORT cannot determine the file size accurately, and what to do about it.