Mainframe sort merge

The Sort/Merge utility is a mainframe program to sort records in a file into a specified order, merge pre-sorted files into a sorted file, or copy selected records. Internally, these utilities use one or more of the standard sorting algorithms, often with proprietary fine-tuned code.

Mainframes were originally supplied with limited main memory by today's standards. The amount of data to be sorted was frequently very large. Because of this, unlike more recent sort programs, early sort/merge programs placed great emphasis on efficient techniques for sorting data on secondary storage, typically tape or disk. In 1968 the OS/360 Sort/Merge program provided five different "sequence distribution techniques" that could be used depending on the number and type of devices available.

Sort/Merge is very frequently used; often the most commonly used application program in a mainframe shop.

Modern sort/merge programs also can copy files, select or omit certain records, summarize records, remove duplicates, reformat records, append new data and produce reports. Indeed most "Sort/Merge" applications use the wide range of additional processing capabilities, rather than purely sorting or merging records: The Sort/Merge product is a very fast way of performing input to and output from these functions.

Sort/merge is important enough that there are multiple companies each selling their own sort/merge package for IBM mainframes and their z/OS, z/VM and z/VSE operating systems. The major Sort/Merge packages are:

• DFSORT sold by IBM.
• SyncSort sold by Syncsort, Inc.
• CA-SORT sold by CA Technologies.

(Some of these also sell versions for other platforms, such as Unix, Linux, or Windows.)

External links

• IBM DFSORT Manuals

See also

• There is also a discussion of mainframe sorting in the BatchPipes article.