Virtual Storage Access Method: Difference between revisions

Revision as of 09:14, 4 April 2007

Revision as of 14:08, 5 April 2007

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VSAM records can be of fixed or variable length. They are organised in fixed-size blocks called Control Intervals (CIs), and then into larger divisions called Control Areas (CAs). Control Interval sizes are measured in bytes — for example 4 [[kilobyte]]s — while Control Area sizes are measured in disk tracks or cylinders.

The utility program IDCAMS is commonly used to manipulate ("delete and define") VSAM [[datasetsdataset]]s. Custom programs can access VSAM datasets through data definitions (DDs) in Job Control Language ([[Job Control Language|JCL]]) or in online regions such as in Customer Information Control Systems ([[CICS]]).

Both [[IMS/DB]] and [[IBM DB2|DB2]] are implemented on top of VSAM and use its underlying [[Data_structure|data structures]].