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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.
The operation of SORT is directed by control statements, which are largely compatible among various IBM and third-party sort programs. The SORT or MERGE statement defines the sort keys— the fields on which the data is to be sorted or merged. This statement identifies the position, length, and data type of each key.
Software for this model did not include an operating system—the RCA 70/15 Programming System consisted of an "Assembly System, Loader Routines, Input-Output Control, Test Routines, Utility Routines, Communication Control, System Maintenance Routines, Report Program Generator, and Sort/Merge." Sort/Merge required a system with 8 KB of memory.
In IBM mainframe operating systems OS/360 and its successors, a Unit Control Block (UCB) is a memory structure, or a control block, that describes any single input/output peripheral device (unit), or an exposure (alias), to the operating system.
In the context of IBM mainframe computers in the S/360 line, a data set (IBM preferred) or dataset is a computer file having a record organization. Use of this term began with, e.g., DOS/360, OS/360, and is still used by their successors, including the current z/OS. Documentation for these systems historically preferred this term rather than file.
The S/360-67 was intended to satisfy the needs of key time-sharing customers, notably MIT (where Project MAC had become a notorious IBM sales failure), the University of Michigan, General Motors, Bell Labs, Princeton University, the Carnegie Institute of Technology (later Carnegie Mellon University), [2] and the Naval Postgraduate School.
The sort ends with a single k-way merge, rather than a series of two-way merge passes as in a typical in-memory merge sort. This is because each merge pass reads and writes every value from and to disk, so reducing the number of passes more than compensates for the additional cost of a k -way merge.
IBM 1800 mainframe. IBM 1800 with its covers open. Unlike the 1130, which was a desk-like unit, the 1800 is packaged in 6 foot high, EIA Standard 19 inch racks, which are somewhat taller than the racks used by S/360 systems of the same vintage, but the internal gates and power supplies were very much the same.