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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.
Job Control Language (JCL) is a scripting language used on IBM mainframe operating systems to instruct the system on how to run a batch job or start a subsystem. [1] The purpose of JCL is to say which programs to run, using which files or devices [2] for input or output, and at times to also indicate under what conditions to skip a step.
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.
A sort is a special case: all the input records must be read before the first output record can be written. Hence there can be no overlap between the input and output phases of a sort. But the input phase can be overlapped with the previous job's output phase. Similarly, the output phase of sort can be overlapped with a downstream job that ...
For example, TSO on z/OS systems uses CLIST or Rexx as command languages along with JCL for batch work. On other systems these may be the same. On other systems these may be the same. The Non-IBM JCL of what at one time was known as the BUNCH (Burroughs, Univac/Unisys, NCR, Control Data, Honeywell), except for Unisys , are part of the BANG [ 3 ...
The program used in the JCL does not actually need to use the files to cause their creation or deletion — the DD DISP=... specification does all the work. Thus a very simple do-nothing program was needed to fill that role. IEFBR14 can thus be used to create or delete a data set using JCL.
An example is the BLKSIZE= variable, which may be (and usually is) specified in the DCB as zero. In the DD statement, the BLKSIZE is specified as a non-zero value and this, then, results in a program-specified LRECL (logical record length) and a JCL-specified BLKSIZE (physical block size), with the merge of the two becoming the permanent ...
This sort of convention is still in active use in mainframes dependent upon JCL and is also seen in the 8.3 (maximum eight characters with period separator followed by three character file type) MS-DOS style.