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

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7.16 Define sharing control data sets<br />

CICS<br />

R/W<br />

CICS<br />

R/W<br />

Batch<br />

R/O<br />

<strong>System</strong> 1<br />

SMSVSAM<br />

address space<br />

SMSVSAM<br />

data space<br />

Primary<br />

SHCDS<br />

Figure 7-18 VSAM RLS sharing control data sets<br />

VSAM RLS sharing control data sets<br />

The sharing control data set (SHCDS) is designed to contain the information required for<br />

DFSMS to continue processing with a minimum <strong>of</strong> unavailable data and no corruption <strong>of</strong> data<br />

when failures occur. The SCDS data can be either SMS or non-SMS managed.<br />

The SHCDS contains the following:<br />

► Name <strong>of</strong> the CF lock structure in use<br />

► <strong>System</strong> status for each system or failed system instance<br />

► Time that the system failed<br />

► List <strong>of</strong> subsystems and their status<br />

► List <strong>of</strong> open data sets using the CF<br />

► List <strong>of</strong> data sets with unbound locks<br />

► List <strong>of</strong> data sets in permit non-RLS state<br />

Defining sharing control data sets<br />

The SHCDS is a logically partitioned VSAM linear data set. Consider the following for the<br />

SHCDS allocation:<br />

► At a minimum, define and activate two SHCDSs and at least one spare SHCDS for<br />

recovery purposes to ensure duplexing <strong>of</strong> your data.<br />

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

CACHE02<br />

CACHE01<br />

IGWLOCK00<br />

Coupling Facility<br />

Secondary<br />

SHCDS<br />

Spare<br />

SHCDS<br />

<strong>Volume</strong>1 <strong>Volume</strong>2 <strong>Volume</strong>3<br />

SMSVSAM<br />

address space<br />

SMSVSAM<br />

data space<br />

<strong>System</strong> 2<br />

SHCDS name: SYS1.DFPSHCDS.qualifier.Vvolser<br />

CICS<br />

R/W<br />

CICS<br />

R/W<br />

Batch<br />

R/O

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