VSAM

Using VSAM, an enterprise can organize records in a file in physical sequence (the sequential order that they were entered), logical sequence using a key (for example, the employee ID number), or by the relative record number on direct access storage devices (DASD).

There are four types of VSAM data sets:

1. Entry Sequenced Data Set (ESDS)
2. Key Sequenced Data Set (KSDS)
3. Linear Data Set (LDS)
4. Relative Record Data Set (RRDS)

IBM now promotes DB2, a relational database management system, although VSAM linear datasets are still used to contain tablespaces and indexspaces within the system. Keyed sequence VSAM is also used by DB2 for the Boot Strap Dataset (BSDS).

Read more about VSAM: - IBM Redbooks has a downloadable guide to VSAM available online. - DBAzine.com has an article that debates the merits of VSAM vs. DB2.

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