Specifying CICS system initialization parameters

You can use the CICS® system initialization parameters to modify CICS system attributes when you start your CICS regions. Different methods are available to define the parameters to CICS. Each system initialization parameter is described, including the syntax and a detailed description.

The information defined by system initialization parameters can be grouped into three categories:
  1. Information used to initialize and control CICS system functions (for example, information such as the dynamic storage area limits and the region exit time interval)
  2. Module suffixes used to load your own versions of CICS control tables (for example, DFHMCTxx)
  3. Special information used to control the initialization process

The primary method of providing system initialization parameters is with a system initialization table (SIT). The parameters of the SIT, which you assemble as a load table, supply the system initialization program with most of the information necessary to initialize the system to suit your unique environment. You can generate more than one SIT, and at the time of system initialization select the one that is appropriate to your needs.

You can also specify other system initialization parameters, which cannot be coded in the SIT. You can specify which SIT you want, and other system initialization parameters (with a few exceptions), in any of three ways:
  1. In the PARM parameter of the EXEC PGM=DFHSIP statement
  2. In the SYSIN data set defined in the startup job stream
  3. Through the system operator's console

You can also use these methods of input to the system initialization process to override most of the system initialization parameters assembled in the SIT.

Some system initialization parameters cannot be coded in the SIT; other parameters cannot be specified in any other way. Finally, some system initialization parameters cannot be specified through the system operator's console. For a summary of the parameters and how they can be specified, see System initialization parameter descriptions and summary.

When you upgrade to a new CICS release

When you upgrade to a new CICS release, if you have existing system initialization tables, you must modify them. Remove all obsolete parameters, and specify the required values for new or changed parameters if you want to run with other than the defaults. When you have made the necessary changes, reassemble the tables using the CICS Transaction Server for z/OS®, Version 5 Release 5 macro libraries.

If you have system initialization parameters defined in CICS startup procedures, you must modify these also.

To avoid generating specific system initialization tables for each CICS region, a simple solution is to let CICS load the default, unsuffixed table (DFHSIT) at startup, and supply the system initialization parameters for each region in a SYSIN data set. For more information about the source of the default system initialization table, see The default system initialization table.