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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.
IEFBR14 is a dummy program, normally inserted in JCL when the only desired action is allocation or deletion of datasets. An example of an IEFBR14 step: // IEFBR14 JOB ACCT , 'DELETE DATASET' // STEP01 EXEC PGM = IEFBR14 // DELDD DD DSN = xxxxx . yyyyy . zzzzz , // DISP = ( MOD , DELETE , DELETE ), UNIT = DASD
IEFBR14 was created because while DD statements can create or delete files easily, they cannot do so without a program to be run due to a certain peculiarity of the Job Management system, which always requires that the Initiator actually execute a program, even if that program is effectively a null statement. [2]
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 .
That is, Unix programs using fopen() can access an MVS dataset and a user can allocate a Unix file as though it were a dataset, with some [NB 5] restrictions. The Hierarchical File System (HFS) (not to be confused with Apple's Hierarchical File System ) uses a unique type of dataset, while the newer z/OS File System (zFS) (not to be confused ...
Virtual Storage Access Method (VSAM) [1] is an IBM direct-access storage device (DASD) file storage access method, first used in the OS/VS1, OS/VS2 Release 1 (SVS) and Release 2 (MVS) operating systems, later used throughout the Multiple Virtual Storage (MVS) architecture and now in z/OS.
Connect:Direct file transfers can be done in two formats: Binary mode (where no translation occurs) or in a mode where translation is used to convert an ASCII file to EBCDIC as it is moved to a mainframe or vice versa. These conversions are handled automatically based on the local systems, which is a significant concern with other file transfer ...
Many of the constants and variables contained within a DCB may be left blank (i.e., these default to zero). The OPEN process results in a merge of the constants and variables specified in the DD JCL statement, and the dataset label for existing magnetic tape and direct-access datasets, into the DCB, replacing the zero values with actual, non-zero values.