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

Cache structures
Coupling Facility cache structures provide a level of storage hierarchy between local memory
and DASD cache.
They are also used as system buffer pool with cross-invalidation being done (see 7.8,
“Buffering under VSAM RLS” on page 388).
Each Coupling Facility cache structure is contained in a single Coupling Facility. You may
have multiple Coupling Facilities and multiple cache structures.
The minimum size of the cache structure is 10 MB.
Sizing the lock and cache structure
For information about sizing the CF lock and cache structure for VSAM RLS, see:
► z/OS DFSMStvs Planning and Operation Guide, SC26-7348
► z/OS DFSMSdfp Storage Administration Reference, SC26-7402
A sizing tool known as CFSIZER is also available on the IBM Web site at:
http://www-1.ibm.com/servers/eserver/zseries/cfsizer/vsamrls.html
Defining Coupling Facility structures
Use CFRM policy definitions to specify an initial and maximum size for each Coupling Facility
structure. DFSMS uses the initial structure size you specify in the policy each time it connects
to a Coupling Facility cache structure.
//STEP10 EXEC PGM=IXCMIAPU
//SYSPRINT DD SYSOUT=A
//SYSABEND DD SYSOUT=A
//SYSIN DD *
DATA TYPE(CFRM) REPORT(YES)
DEFINE POLICY NAME(CFRM01) REPLACE(YES)
STRUCTURE NAME(CACHE01)
SIZE(70000)
INITSIZE(50000)
PREFLIST(CF01,CF02)
STRUCTURE NAME(CACHE02)
SIZE(70000)
INITSIZE(50000)
PREFLIST(CF01,CF02)
STRUCTURE NAME(IGWLOCK00)
SIZE(30000)
INITSIZE(15000)
PREFLIST(CF01,CF02)
/*
Figure 7-15 Example of defining VSAM RLS CF structure
Displaying Coupling Facility structures
You can use the system command DISPLAY XCF to view your currently defined Coupling
Facility structures. An example of XCF display of the lock structure is in Figure 7-16 on
page 399.
398 ABCs of z/OS System Programming Volume 3