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While backwards compatibility was maintained, the older access methods suffered from performance problems due to the address translation required for virtual storage. The KSDS organization was designed to replace ISAM, the Indexed Sequential Access Method. Changes in disk technology had meant that searching for data in ISAM data sets had become ...
5740-XYQ Data Facility Extended Function (DFEF) 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
An access method is a function of a mainframe operating system that enables access to data on disk, tape or other external devices. Access methods were present in several mainframe operating systems since the late 1950s, under a variety of names; the name access method was introduced in 1963 in the IBM OS/360 operating system. [ 1 ]
Indexed Sequential Access Method (ISAM) is a method for creating, maintaining, and manipulating computer files of data so that records can be retrieved sequentially or randomly by one or more keys. Indexes of key fields are maintained to achieve fast retrieval of required file records in indexed files .
A virtual storage area network (virtual SAN, VSAN or vSAN) is a logical representation of a physical storage area network (SAN). A VSAN abstracts the storage-related operations from the physical storage layer, and provides shared storage access to the applications and virtual machines by combining the servers' local storage over a network into a single or multiple storage pools.
In the mid-1970s IBM introduced MVS, which not only supported virtual storage that was larger than the available real storage, [NB 2] as did SVS, but also allowed an indefinite number of applications to run in different address spaces. Two concurrent programs might try to access the same virtual memory address, but the virtual memory system ...
6 So why was "Virtual Storage Access Method" wrong? 1 comment. 7 American-Express. 8 Requested move 2 October 2017. 7 comments. Toggle the table of contents.
A single-file virtual file system may include all the basic features expected of any file system (virtual or otherwise), but access to the internal structure of these file systems is often limited to programs specifically written to make use of the single-file virtual file system (instead of implementation through a driver allowing universal ...