z/OS DFSMS Using Data Sets
z/OS DFSMS Using Data Sets
Previous topic |
Next topic |
Contents |
Contact z/OS |
Library |
PDF
Prime Index z/OS DFSMS Using Data Sets SC23-6855-00 |
|
A key-sequenced data set always has a prime index that relates
key values to the relative locations of the logical records in a data
set. The prime index, or simply index, has two uses in locating:
When initially loading a data set, records must be presented to VSAM in key sequence. The index for a key-sequenced data set is built automatically by VSAM as the data set is loaded with records. When a data control interval is completely loaded with logical records, free space, and control information, VSAM makes an entry in the index. The entry consists of the highest possible key in the data control interval and a pointer to the beginning of that control interval. 
|
 Copyright IBM Corporation 1990, 2014 |
