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On OS/360 and derived mainframe systems, most programs never specify files (usually called datasets) directly, but instead reference them indirectly through the Job Control Language (JCL) statements that invoke the programs. These data definition (or "DD") statements can include a "disposition" (DISP=...
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.
Changing the physical block size or logical record length of a sequential data set. Creating an edited data set. Printing a sequential data set or a member of a PDS. Creating partitioned output data set from sequential input data set. An example of an IEBGENER program to copy one dataset to another:
A partitioned data set (PDS) [7] is a data set containing multiple members, each of which holds a separate sub-data set, similar to a directory in other types of file systems. This type of data set is often used to hold load modules (old format bound executable programs), source program libraries (especially Assembler macro definitions), ISPF ...
Custom programs can access VSAM datasets through Data Definition (DD) statements in Job Control Language (JCL), via dynamic allocation or in online regions such as in Customer Information Control System (CICS). Both IMS/DB [citation needed] and Db2 [2]: 41 [6] are implemented on top of VSAM and use its underlying data structures.
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 ...
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 ...
JCL is used to define jobs to both JES2 and JES3, but small changes usually need to be made to the JCL to get a job written for one JES to run on the other. A common issue was that JES3 checked that all datasets listed in the JCL existed before execution or that there was a prior step where the dataset was defined as NEW,CATLG.