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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.
Files, other than Unix files, are properly called data sets in MVS. Names of those files are organized in catalogs that are VSAM files themselves. Data set names (DSNs, mainframe term for filenames) are organized in a hierarchy whose levels are separated with dots, e.g. "DEPT01.SYSTEM01.FILE01".
DFSMS/MVS also replaced utilities and service aids. DSDSS and DFHSM became optional chargeable features of DFSMS; DFSORT and RACF remained separate products. While DFSMS/MVS Release 1 still included ISAM, IBM eventually dropped it, but continued to support the ISAM compatibility interface to VSAM.
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.
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.
A key-sequenced data set (KSDS) is a type of data set used by IBM's VSAM computer data storage system. [ 1 ] : 5 Each record in a KSDS data file is embedded with a unique key. [ 1 ] : 20 A KSDS consists of two parts, the data component and a separate index file known as the index component which allows the system to physically locate the record ...
The Distributed File Management (DFM) [8] project was initiated to add DDM services to IBM's MVS operating system to enable programs on remote computers to create, manage, and access VSAM files. John Hufferd, the manager of the DFM project looked to the DDM Architecture team for a means of converting the data fields in records as they flowed ...
Although GenevaERS can access multiple types of mainframe-based data, including Db2 and VSAM, like MapReduce, GenevaERS's higher performance comes with the use of sequential files. GenevaERS processes are called VIEWSs, and any number of VIEWs can be run in one pass of the data.