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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.
The previous example is a two-pass sort: first sort, then merge. 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 ...
It added virtual memory in support of the new System/370 series hardware. It used a fixed page table which mapped a single address space of up to 16 megabytes for all partitions combined. DOS/VS increased the number of partitions (separate simultaneous programs) from three (named Background, Foreground 1 and Foreground 2) to five (BG and F1 ...
An example of such is the classic merge that appears frequently in merge sort examples. The classic merge outputs the data item with the lowest key at each step; given some sorted lists, it produces a sorted list containing all the elements in any of the input lists, and it does so in time proportional to the sum of the lengths of the input ...
Repeatedly merge sublists to create a new sorted sublist until the single list contains all elements. The single list is the sorted list. The merge algorithm is used repeatedly in the merge sort algorithm. An example merge sort is given in the illustration. It starts with an unsorted array of 7 integers. The array is divided into 7 partitions ...
In IBM mainframe operating systems, such as OS/360, MVS, z/OS, a Data Control Block (DCB) is a description of a dataset in a program. A DCB is coded in Assembler programs using the DCB macro instruction (which expands into a large number of "define constant" instructions). High level language programmers use library routines containing DCBs.
VME (Virtual Machine Environment) is a mainframe operating system developed by the UK company International Computers Limited (ICL, now part of the Fujitsu group). Originally developed in the 1970s (as VME/B, later VME 2900) to drive ICL's then new 2900 Series mainframes, the operating system is now known as OpenVME incorporating a Unix subsystem, and runs on ICL Series 39 and Trimetra [1 ...