Defining the global catalog

The global catalog is a VSAM key-sequenced data set (KSDS) is used to store start type information, location of the CICS system log, resource definitions, terminal control information and profiles.

About this task

CICS uses the global catalog to perform the following activities:

To record information that governs the possible types of start and the location of the CICS system log.
During the running of CICS, to hold the resource definitions that are installed during initialization when CICS installs the group list, by the RDO CEDA INSTALL command or by the EXEC CICS CREATE command.
During a normal shutdown, to record terminal control information and profiles. All other warm keypoint information is written to the CICS system log.

You must ensure that the REGION parameter on your CICS jobs is high enough to cope with the increase in buffer storage used for the global catalog, because this storage comes out of region storage not EDSA.

You can define and initialize the CICS global catalog in two ways. You can use the sample job as described below, or you can use the CICS-supplied job, DFHDEFDS.

Edit the sample job:

Procedure

Edit the data set name in the CLUSTER definition to be the same as the DSN parameter in the DD statement for the global catalog in the CICS startup job stream.
The primary and secondary extent sizes are shown as n1 and n2 cylinders. Calculate the size required to meet your installation requirements, and substitute your values for n1 and n2.
Whichever IDCAMS parameter you use for the global catalog data set space allocation (CYLINDERS, TRACKS, or RECORDS), make sure that you specify a secondary extent. CICS abends if your global catalog data set fills and VSAM cannot create a secondary extent. For information about record sizes, see Table 1
Specify the REUSE option on the DEFINE CLUSTER command.
This option enables the global catalog to be opened repeatedly as a reusable cluster. Also specify REUSE if you intend to use the COLD_COPY input parameter of the DFHRMUTL utility.
Edit the CONTROLINTERVALSIZE values for the VSAM definition if required.
This job does not specify a minimum or maximum buffer size explicitly, but accepts the default that is set by VSAM. You can code an explicit value if you want to define buffers of a specific size. See Buffer space sizings for more information.
Use the recovery manager utility program, DFHRMUTL, to initialize the data set. Specify this utility in the job step INITGCD.
DFHRMUTL writes a record to the data set, specifying that on its next run using this global catalog, if START=AUTO is specified, CICS is to perform an initial start and not prompt the operator for confirmation. This record is called the autostart override record.
Add a job step to run the DFHCCUTL utility.
Adding this step means that the global and local catalogs do not get out of step.
Define the data definition statement for CICS as:
```
//DFHGCD  DD  DSN=CICSTS53.CICS.applid.DFHGCD,DISP=OLD
```
This example shows the minimum specification for a global catalog for use by a single CICS region.
Add the relevant AMP subparameters to the DD statement to help improve restart and shutdown time.
The AMP parameter is described in z/OS MVS JCL Reference and an example is shown in the CICS startup job stream in CICS startup.

Example

Figure 1. Example job to define and initialize the global catalog

//GLOCAT   JOB accounting info,,CLASS=A
//DEFGCD   EXEC PGM=IDCAMS
//SYSPRINT DD   SYSOUT=*
//SYSIN    DD   *
      DEFINE CLUSTER -
               (NAME(CICSTS53.CICS.applid.DFHGCD) -               
               INDEXED                      -
               CYLINDERS(n1 n2)             -                     
               FREESPACE(10 10)             -
               SHAREOPTIONS(2)              -
               RECORDSIZE(4089 32760)       -
               REUSE                        -                     
               VOLUMES(volid))              -
             DATA                           -                     
               (NAME(CICSTS53.CICS.applid.DFHGCD.DATA)  -
               CONTROLINTERVALSIZE(32768)    -                     
               KEYS(52 0))                  -
             INDEX                          -
               (NAME(CICSTS53.CICS.applid.DFHGCD.INDEX) )
/*
//INITGCD  EXEC PGM=DFHRMUTL,REGION=1M                            
//STEPLIB  DD DSNAME=CICSTS53.CICS.SDFHLOAD,DISP=SHR
//SYSPRINT DD SYSOUT=A
//DFHGCD   DD DSNAME=CICSTS53.CICS.applid.DFHGCD,DISP=OLD
//SYSIN    DD *
SET_AUTO_START=AUTOINIT
/*