Data Sets in VSAM - Virtual Storage Access Method

Entry Sequenced Data Set

Records in an ESDS are stored in the order in which they are written and are retrived by addressed access.

ESDS is a sequential VSAM data set.

Key Sequenced Data set - KSDS

Rrecords in a KSDS are stored in key sequence and are controlled by an index, determine the order in which records are stored.

In KSDS, records can be processed both sequentially and randamly.

Relative Record Data Sets - RRDS

Records in an RRDS are located into fixed length or veriable length slots. These record are represented by the Relative Record Numbers(RRN) of their slots.

Records are accessed based on their original position in th file.

Linear Data Sets

LDS is an unstructured VSAM dataset. LDS is a data set containing only a contiguous string of data bytes with no intervening control information.