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A Generation Data Group [10] (GDG) [11] is a group of non-VSAM data sets [12] that are successive generations of historically-related data [13] stored on an IBM mainframe (running OS or DOS/VSE). [14] A GDG is usually cataloged. [13] An individual member of the GDG collection is called a "Generation Data Set."
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:
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.
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=...
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.
Modern versions of MVS (e.g., z/OS) use datasets as containers for Unix filesystems along with facilities for partially integrating them. 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.
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.
Dataset creation date (binary) one byte for year of century and two bytes for day-of-year 56: 3: Dataset expiration date (same format as creation date) 99365 indicates that this dataset will never expire. 59: 1: Number of extents for this dataset (binary) 60: 1: If this dataset is a partitioned dataset this is the number of bytes used in the ...