This section describes the CICS® system initialization parameters, which you can use to modify CICS system attributes when you start your CICS regions. It gives the syntax and a detailed description of each system initialization parameter, and describes the methods that you can use to define the parameters to CICS.
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 specify which SIT you want, and other system initialization parameters (with a few exceptions), in any of three ways:
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.
The information defined by system initialization parameters can be grouped into three categories:
The syntax of the system initialization parameters that can be coded in the DFHSIT macro is listed in Table 17. Except for those parameters marked "SIT macro only", all the system initialization parameters can be provided at run time, although there are restrictions in some cases. The restrictions are explained at the end of the description of the system initialization parameter to which they apply. See the CHKSTRM parameter in topic CHKSTRM for an example of such a restriction.
There are some other CICS system initialization parameters (and options of the parameters in Table 17) that you cannot define in the DFHSIT macro. (See Initialization parameters that cannot be coded in the DFHSIT macro.) The parameters that you cannot define in the DFHSIT macro are shown in Figure 33.
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 3 Release 1 macro libraries.
If you have system initialization parameters defined in CICS start-up 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 start-up, 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.