Transcription of Chapter 28: Virtual Storage Access Method (VSAM)
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Chapter 28: Virtual Storage Access Method (VSAM)
Page496 Chapter 28 Revised January 19, 2010 Copyright 2009 byEdward L. Bosworth, 28: Virtual StorageAccess Method ( vsam )Author s Note:This Chapter is copied almost verbatim from the material inChapter19of the textbook by Peter is used by ( vsam ) is a relatively recent file organization methodfor users of IBMOS/VS and facilitates both sequential andrandomprocessing and supplies a number of useful utility termfileis somewhat ambiguous since it may reference an I/O device orthe recordsthat the device processes. To distinguish a collection of records,IBMOS literature usesthe termdata provides three types of data sets:1. Key-sequenced Data Set (KSDS).KSDS maintains records in sequence ofkey, such asemployee or part number, and is equivalent to indexed sequentialaccess Method (ISAM).2. Entry-sequenced Data Set (ESDS).ESDS maintains records in the sequencein whichthey were initially entered and is equivalent to sequential Relative-Record Data Set (RRDS).
S/370 Assembler VSAM Page 498 Chapter 28 Revised January 19, 2010 Copyright © 2009 by Edward L. Bosworth, Ph.D. • Choose one entry to designate the type of data ...
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