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ABCs of z/OS System Programming Volume 3 - IBM Redbooks

ABCs of z/OS System Programming Volume 3 - IBM Redbooks

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6.3 The VSAM volume data set (VVDS)<br />

Three types <strong>of</strong> entries in a VVDS<br />

One VSAM volume control record (VVCR)<br />

Contains control information about BCSs which have<br />

data sets on this volume<br />

Multiple VSAM volume records (VVR)<br />

Contain information about the VSAM data sets on<br />

that volume<br />

Multiple non-VSAM volume records (NVR)<br />

Contain information about the non-VSAM data set<br />

on that volume<br />

VVDS is a VSAM entry-sequenced data set (ESDS)<br />

Data set name: SYS1.VVDS.Vvolser<br />

Can be defined explicitly or implicitly<br />

Figure 6-3 The VSAM volume data set<br />

The VSAM volume data set (VVDS)<br />

The VSAM volume data set (VVDS) contains additional catalog information (not contained in<br />

the BCS) about the VSAM and SMS-managed non-VSAM data sets residing on the volume<br />

where the VVDS is located. Every volume containing any VSAM or any SMS-managed data<br />

sets must have a VVDS on it. The VVDS acts as a kind <strong>of</strong> VTOC extension for certain types <strong>of</strong><br />

data sets. A VVDS can have data set information about data sets cataloged in distinct BCSs.<br />

Entry types in the VVDS<br />

There are three types <strong>of</strong> entries in a VVDS. They are:<br />

► VSAM volume control records (VVCR)<br />

– First logical record in a VVDS<br />

– Contain information for management <strong>of</strong> DASD space and the names <strong>of</strong> the BCSs that<br />

have data sets on the volume<br />

► VSAM volume records (VVR)<br />

– Contain information about a VSAM data set residing on the volume<br />

– Number <strong>of</strong> VVRs varies according to the type <strong>of</strong> data set and the options specified for<br />

the data set<br />

– Also included are data set characteristics, SMS data, extent information<br />

– There is one VVR describing the VVDs itself<br />

330 <strong>ABCs</strong> <strong>of</strong> z/<strong>OS</strong> <strong>System</strong> <strong>Programming</strong> <strong>Volume</strong> 3

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