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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".
DFEF offers a new type of VSAM catalog, but had reliability problems that were only resolved in DFP. 5740-AM3 Sequential Access Method Extended (SAM-E) SAM-E improves the performance of BPAM, BSAM and QSAM on direct access storage devices. 5740-AM8 Access Method Services Cryptographic Option 5748-UT2 Offline 3800 Utility
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.
IDMS organizes its databases as a series of files. These files are mapped and pre-formatted into so-called areas. The areas are subdivided into pages which correspond to physical blocks on the disk. The database records are stored within these blocks. The DBA allocates a fixed number of pages in a file for each area.
Basic Direct Access Method, or BDAM is an access method for IBM's OS/360 and successors computer operating systems on System/360 and later mainframes.BDAM "consists of routines used in retrieving data from, and storing data onto, direct access devices."
RMS provides an additional layer between the application and the files on disk that provides a consistent method of data organization and access across multiple 3GL and 4GL languages. RMS provides four different methods of accessing data; sequential, relative record number access, record file address access, and indexed access.
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 ...