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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.
IDCAMS was introduced along with VSAM in OS/VS; the "Access Method" reference derives from the initial "VSAM replaces all other access methods" mindset of OS/VS. IDCAMS probably has the most functionality of all the utility programs, performing many functions, for both VSAM and non-VSAM files.
An entry-sequenced data set (ESDS) is a type of data set used by IBM's VSAM computer data storage system. [1]: 5 Records are accessed based on their sequential order, that is, the order in which they were written to the file; which means that accessing a particular record involves searching all the records sequentially until it is located, or by using a relative physical address (Relative byte ...
A relative record data set (RRDS) is a type of data set organization used by IBM's VSAM computer data storage system. [1]: 5 Records are accessed based on their ordinal position in the file (relative record number, RRN). [1]: 29 For example, the desired record to be accessed might be the 42nd record in the file out of 999 total.
File status okay; about to open data connection. 200 Series: The requested action has been successfully completed. 202: Command not implemented, superfluous at this site. 211: System status, or system help reply. 212: Directory status. 213: File status. 214: Help message. Explains how to use the server or the meaning of a particular non ...
VSAM also included a catalog component used for user catalogs and MVS' master catalog. Partitioned data sets (PDS) are sequential data sets subdivided into "members" that could each be processed as sequential files in their own right (like a folder in a file system). The most important use of PDSes was for program libraries - system ...
M is the extent number for files with more than one extent (non-contiguous files). BB is zero. Previously this indicated the bin on an IBM 2321 Data Cell. CC is the absolute cylinder number on the device. HH is the track (head) number. R is the record number on the track. Record zero contains control information for the track and can not be used.
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]