Defining coupling facility structures

Before you enable Db2 data sharing, you must define coupling facility structures.

Before you begin

Tip: You can use the coupling facility structure sizer (CFSizer) tool to help you calculate CF structure storage sizes for Db2 data sharing. For more information, see The CFSizer tool .

About this task

You must define one lock structure, one list structure, and at least four cache structures:

Group buffer pool 0
Group buffer pool 8K0
Group buffer pool 16K0
Group buffer pool 32K

The lock structure and list structures (SCAs) do not need to be in the same coupling facility. Individual structures cannot span coupling facilities.

Recommendation: Use a Sysplex Failure Management (SFM) policy to define the availability characteristics of the coupling facility structures for lost connectivity failures, which includes a total failure of the coupling facility.

Procedure

To define coupling facility structures:

Determine the following characteristics of your Db2 coupling facility structures:

Initial size and maximum size of the structures

The structures can be dynamically re-sized from INITSIZE up to the value in SIZE.

Structure names

Determine the names that you will use for the coupling facility structures.

Availability characteristics

You must know the preference list (PREFLIST) for rebuilding or reallocating a structure, if the coupling facility fails.
Create coupling facility resource management (CFRM) policies to define the structures to the Parallel Sysplex®, and define an SFM policy to specify actions when certain failures occur in the sysplex.
A CFRM policy determines how and where coupling facility structure resources are allocated. You can use the administrative data utility (IXCMIAPU) to define the CFRM and SFM policies. For more information, seeManaging coupling facility resources and Controlling system availability and recovery through the SFM Policy .

Example

A sample CFRM policy is shown in the following figure.

Figure 1. Sample CFRM policy

//POLICYX  JOB MSGCLASS=Z,REGION=2000K,CLASS=A,
//             MSGLEVEL=(1,1)
//STEP1  EXEC PGM=IXCMIAPU
//STEPLIB DD DSN=SYS1.MIGLIB,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSIN  DD *
 DATA TYPE(CFRM) REPORT(YES)
 DEFINE POLICY NAME(POLICYX) REPLACE(YES)
   STRUCTURE NAME(DSNDB0A_LOCK1)
             INITSIZE(32000)
             SIZE(64000)
             REBUILDPERCENT(5)
             PREFLIST(CF01,CF02)
   STRUCTURE NAME(DSNDB0A_GBP0)
             INITSIZE(50000)
             SIZE(100000)
             REBUILDPERCENT(5)
             DUPLEX(ALLOWED)
             PREFLIST(CF02,CF01)
   STRUCTURE NAME(DSNDB0A_GBP1)
             INITSIZE(50000)
             SIZE(100000)
             PREFLIST(CF02,CF01)
             DUPLEX (ENABLED)
   STRUCTURE NAME(DSNDB0A_SCA)
             INITSIZE(10000)
             SIZE(20000)
             REBUILDPERCENT(5)
             PREFLIST(CF01,CF02)
 
   CF NAME(CF01) TYPE(009674)
                 MFG(IBM)
                 PLANT(00)
                 SEQUENCE(000000040016)
                 PARTITION(1)
                 CPCID(00)
                 DUMPSPACE(1200)
 
   CF NAME(CF02) TYPE(009674)
                 MFG(IBM)
                 PLANT(00)
                 SEQUENCE(000000040029)
                 PARTITION(1)
                 CPCID(00)
                 DUMPSPACE(1200)
//