A named counter is stored in a named counter pool, which resides in a list structure in a coupling facility. Each pool, even if its list structure is defined with the minimum size of 256KB, can hold up to a thousand named counters.
You create a named counter pool by defining the coupling facility list structure for the pool, and then starting the first named counter server for the pool. Pool names are of 1 to 8 bytes from the same character set for counter names. Although pool names can be made up from any of the allowed characters, names of the form DFHNCxxx are recommended.
You can create different pools to suit your needs. You could create a pool for use by production CICS® regions (for example, called DFHNCPRD), and others for test and development regions (for example, using names like DFHNCTST and DFHNCDEV). See Named counter options table for information about how you can use logical pool names in your application programs, and how these are resolved to actual pool names at runtime.
Defining a list structure for a named counter server, and starting a named counter server, is explained in the CICS System Definition Guide.
The POOL(name) parameter is optional on all the EXEC CICS COUNTER and DCOUNTER commands (see Using the named counter EXEC interface for more information). If you specify the POOL parameter, it can refer to either an actual or a logical pool name. Whether you specify a POOL parameter or omit it, CICS resolves the actual pool name by reference to the named counter options table, which is loaded from the link list.
The named counter options table, DFHNCOPT, provides several methods for determining the actual pool name referenced by a named counter API command, all of which are described in the CICS System Definition Guide. This also describes the DFHNCO macro that you can use to create your own options table.
This section discusses how the POOLSEL parameter in the default options table works in conjunction with the POOL(name) option on the API. The default options table is supplied in source and object form. The pregenerated version is in hlq.SDFHLINK, and the source version, which is supplied in the hlq.SDFHSAMP library ( where hlq represents the high-level qualifier for the library names, established at CICS installation time), contains the following entries:
DFHNCO POOLSEL=DFHNC*,POOL=YES
DFHNCO POOL=
END DFHNCOPT
The default options table entries work as follows:
You can specify the default pool name to be used by a CICS region by specifying the NCPLDFT system initialization parameter. If NCPLDFT is omitted, the pool name defaults to DFHNC001.
You can see from the above that you do not need to create you own options table, and named counter API commands do not need to specify the POOL option, if: