Virtual Storage Access Method

What Does Virtual Storage Access Method Mean?

Virtual storage access method (VSAM) is a file storage access
method used in IBM mainframes. VSAM is an expanded
version of indexed sequential access method (ISAM), which was the file access method
used previously by IBM.

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Techopedia Explains Virtual Storage Access Method

VSAM enables the organization of records in physical or logical sequences. Files can also be indexed by record number. VSAM helps enterprises by providing quick access to data by the use of the inverted index. The records in VSAM can be either variable or fixed length.

VSAM consists of four major types of data sets (a file is represented by data set by IBM), these include:

  • Key-sequenced data set (KSDS)
  • Relative record data set (RRDS)
  • Entry-sequenced data set (ESDS)
  • Linear data set (LDS)

KSDS, RRDS and ESDS contain records while LDS consists of page sequences.

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.