Using VSAM data sets in a transaction

DFSMStvs supports access to these types of data sets:

Key-sequenced data set (KSDS)
Entry-sequenced data set (ESDS)
Relative record data set (RRDS) (both fixed and variable record lengths)

VSAM data sets are stored on direct access storage devices (DASD). VSAM divides its data set storage into control areas, which are further divided into control intervals. Control intervals are the unit of data transmission between virtual and auxiliary storage. Each one is of fixed size and, in general, contains a number of records. A KSDS or ESDS can have records that extend over more than one control interval. These are called spanned records.