You activate a named counter pool in an MVS™ image by starting up a named counter server region for that pool. You can start the server as a started task, started job, or as a batch job.
The named counter server region program is called DFHNCMN and must be run from an APF-authorized library. DFHNCMN is supplied in the CICS® authorized library, CICSTS31.CICS.SDFHAUTH.
The server reads its initialization parameters from a SYSIN data set, and writes messages and statistics to a print file, for which it requires a SYSPRINT DD statement.
The named counter pool server requires some parameters in the start-up JCL. You can specify these in the PARM string, or in the SYSIN data set, or in a combination of both. When a parameter is specified in both places, the PARM value overrides the SYSIN value (because the PARM can be overridden on the MVS START command).
The most important parameter is the pool name, which is mandatory. Among other things, the pool name is used to form, with the prefix DFHNC, the server name (giving DFHNC.poolname).
The easiest way to ensure that all pool-related parameters are consistent across MVS images is to use the same SYSIN parameter data set (or an identical copy of it) for all servers accessing the same pool, and to specify in the PARM field any parameters that vary between servers.
For details of all the parameters, see Named counter server parameters.
Use the JCL REGION parameter to ensure that the named counter server region has enough storage to process the maximum number of named counter requests that can be executing concurrently.
The named counter server typically uses less than one megabyte of storage above 16MB and less than 20KB below 16MB.
During server initialization, the server acquires all the available storage above 16MB, as determined by the REGION parameter, then releases 5% of it for use by operating system services. It also acquires 5% of the free storage below 16MB for use in routines that require 24-bit addressable storage.
After initialization, the server uses AXM page allocation services to manage its storage. Server statistics indicate how much storage is actually allocated and used within the storage areas above and below 16MB, which are called AXMPGANY and AXMPGLOW in the statistics.
If a task in the server region or a cross-memory request runs out of storage, this is likely to result in AXM terminating that task or request using a simulated abend with system completion code 80A to indicate a GETMAIN failure. Although the server can usually continue processing other requests in this case, running out of storage in a critical routine can cause the server to terminate. Therefore, it is best to ensure that the REGION size is large enough to eliminate this risk.
//MVSnNC1 JOB ...
//NCSERVER EXEC PGM=DFHNCMN,REGION=32M,TIME=NOLIMIT Named counter server
//STEPLIB DD DSN=CICSTS31.CICS.SDFHAUTH,DISP=SHR Authorized library
//SYSPRINT DD SYSOUT=* Messages and statistics
//SYSIN DD *
POOLNAME=MVSnNC1 Pool name
/*
Parameters are specified in the form KEYWORD=value, where keywords can optionally be specified in mixed case to improve readability. If you specify more than one parameter in the PARM field or on the same SYSIN input line, the parameters must be separated by a comma. Any text following one or more spaces is taken as a descriptive comment. Any parameter line which starts with an asterisk or a space is assumed to be a whole line comment.
You can enter some parameter keywords in more than one form, such as in abbreviated or truncated form.
The main parameters are listed on the server print file during start-up.
This parameter, POOLNAME, is always required:
This parameter is valid only at server initialization, and must always be specified.
This keyword can be abbreviated to POOL.
Use the following parameters to specify server statistics options:
The valid range of times is from 00:00 to 24:00.
This keyword can be abbreviated to EOD.
The time interval can range from 00:01 to 24:00.
This keyword can be abbreviated to STATSINT.
This keyword can be abbreviated to STATSOPT.
During server initialization, the server unconditionally registers with ARM except when the server program is invoked with either the UNLOAD or the RELOAD functions. The server will not start if the registration fails.
Use the following parameters to override default processing for the automatic restart manager:
The default identifier is of the form DFHNCnn_poolname, where NC represents the server type, nn is the &SYSCLONE value for the system (which can be either one or two characters), and poolname is the name of the pool served by the server.
This parameter is only valid at server initialization.
This keyword can be abbreviated to ARMELEMENT or ARMELEMNAME.
The default element type is SYSCICSS.
This parameter is only valid at server initialization.
This keyword can be abbreviated to ARMELEMTYPE.
These parameters specify list structure attributes. They are used only for the initial allocation of resources when the pool list structure is being created, which occurs the first time you start a server for a pool.
It is generally preferable to omit this parameter, and specify the structure size using the INITSIZE parameter in the CFRM policy. The POOLSIZE option can, however, be useful if the structure is being reallocated or reloaded, and the CFRM policy has not been updated to reflect the required size.
This parameter is valid only at server initialization and is only used when the structure is first allocated.
These parameters are provided only for intensive debug tracing.
Using these options in a production environment could have a significant impact on performance and cause the print file to grow very rapidly, using up spool space.
Trace messages from cross-memory requests can be lost if they are generated faster than the trace print subtask can print them. In this event, the trace only indicates how many messages were lost.
This keyword can also be specified as TRACECF.
This keyword can also be specified as TRACERQ=.
Use these parameters to modify the thresholds at which warning messages are issued when the structure becomes nearly full.
The valid range is from 1 to 100 per cent.
The valid range is from 1 to 100 per cent.