What is the full form of DASD?

Full form of DASD: Here, we are going to learn what does DASD stands for? DASD – which is an abbreviation of "Direct-Access Storage Device" in Computer Acronyms/Abbreviations, etc.
Submitted by Anushree Goswami, on November 07, 2020

DASD: Direct-Access Storage Device

DASD is an abbreviation of the "Direct-Access Storage Device". It is a magnetic disk-based secondary storage device, which comprises in cooperation permanent and removable media and contains various physical records, each has a separate distinct location and a distinctive address.

Storage device access methods

In DASD, access methods consist of:

  • Sequential access method: It is a method, which access data in a memory in a prearranged, structuredsuccession.
  • Indexed access method: It is a method, which creates, maintains and controls data and accordingly, the records can be taken back in succession through recovery or arbitrarily through single or multiple keys.
  • Direct access method: It is also known as random access method, which access an arbitrary data of a succession in equivalent time almost as simply, effortlessly and proficiently as any other additional method.

CTR

Access I/O devices of IBM computers comprises DASD in the course of channels, which write to, read from, and be in command of the specified device.

CTR is an abbreviation of an eight byte "Cylinder Track Record" block address, or MBBCCHHR, Channel programs address DASD by making use of a six byte seek address (BBCCHH) and a five byte record identifier (CCHHR).

  • M corresponds to the extent number contained by the allocation
  • BBcorresponds to the Bin (from 2321 data cells),
  • CCcorresponds to the Cylinder,
  • HHcorresponds to the Head (or track), and
  • Rcorresponds to the Record (block) number.

Reference: Direct-access storage device


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