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VSAM was introduced in the 1970s when IBM announced virtual storage operating systems (DOS/VS, OS/VS1 and OS/VS2) for its new System/370 series, as successors of the DOS/360 and OS/360 operating systems running on its System/360 computer series. While backwards compatibility was maintained, the older access methods suffered from performance ...
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
Starting in z/OS V1R7, ISAM data sets can no longer be processed (created, opened, copied or dumped). ISAM data sets that are still in use must be converted to VSAM key-sequenced data sets. Prior to z/OS V1R7, you could use access method services to allocate a VSAM key-sequenced data set and copy an ISAM data set into it.
Multiple Virtual Storage, more commonly called MVS, is the most commonly used operating system on the System/370, System/390 and IBM Z IBM mainframe computers. IBM developed MVS, along with OS/VS1 and SVS, as a successor to OS/360. It is unrelated to IBM's other mainframe operating system lines, e.g., VSE, VM, TPF.
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 ...
Basic, in IBM terminology, indicates a lower-level access method that deals with data sets in terms of physical blocks and does not provide either read-ahead, called anticipatory buffering, or synchronization — that is, the user program has to explicitly wait for completion of each input/output event.
The other distinctive features of MVS are: its main catalog must be a VSAM catalog; it supports "tightly-coupled multiprocessing" (2 or more CPUs share the same memory and copy of the operating system); it includes a System Resources Manager (renamed Workload Manager in later versions) which allows users to load additional work on to the system ...
In the context of IBM mainframe computers in the S/360 line, a data set (IBM preferred) or dataset is a computer file having a record organization. Use of this term began with, e.g., DOS/360, OS/360, and is still used by their successors, including the current z/OS. Documentation for these systems historically preferred this term rather than file.