A Summary Of The Characteristics Of VSAM Data Set Types | Comparing VSAM Data Set Organizations.

Characteristics Of VSAM Data Set Types

I hope you have gone through my previous tutorial regarding VSAM terminology and concept. As you are already aware that there are 4 types of VSAM cluster/data sets i.e. KSDS, ESDS, LDS, RRDS.

In this tutorial, I have tried to compare the characteristics of the VSAM data set  (i.e. ESDS, KSDS, RRDS, VRRDS).

This comparison of the VSAM data set organization would help you to understand the difference of each cluster.

The table provides a summary of the characteristics of VSAM data set types. 

ESDS	KSDS	Fixed-length RRDS	Variable-length RRDS	Linear data sets
Records are in the same order as they are entered	Records are in collating sequence by key field after load	Records are in relative record number order	Records are in relative record number order	No processing at a record level
Records can be fixed or variable length	Records can be fixed or variable length	Records are fixed length	Records are variable length	No processing at a record level
Direct access by RBA	Direct access by key or by RBA	Direct access by relative record number	Direct access by relative record number	Access with Data-In-Virtual (DIV) optionally
Consist of a data component only	Consist of data and index components	Consist of a data component only	Consist of data and index components	Consist of a data component only
Alternate index allowed	Alternate indexes allowed	No alternate index allowed	No alternate index allowed	No alternate index allowed
A record’s RBA cannot change	A record’s RBA can change	A record’s relative record number cannot change	A record’s relative record number cannot change	No processing at a record level
Space at the end of the data set is used for adding records	Free space is used for inserting and lengthening records	Empty slots in the data set are used for adding records	Free space is used for inserting and lengthening records	No processing at a record level
A record cannot be deleted, but you can reuse its space for a record of the same length	Space that is given up by a deleted or shortened record becomes free space	A slot that is given up by a deleted record can be reused	Space that is given up by a deleted or shortened record becomes free space	No processing at a record level
Spanned records allowed	Spanned records allowed	No spanned records	No spanned records	No spanned records
Extended format allowed	Extended format or compression allowed	Extended format allowed	Extended format allowed	Extended format allowed