1.3. What is VSAM?

VSAM is one of several access methods in z/OS. It only applies to data stored in DASD devices. An access method is re-entrant code contained in DFSMSdfp™, a component of the DFSMS z/OS product. This access method makes it easier for an application to execute an I/O operation (moving data between an I/O device and memory).

1.3.1. VSAM access types

There are three types of access in VSAM:

  • Random: This is also referred to as direct access. The logical record needs to be located by the use of a search argument coming from the application. There is no search argument connection between two consecutive logical record accesses.

  • Sequential: The entire file is processed (for Read or Write), one logical record after the other. The application ...

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