CICS startup

Depending on your system environment, you can start the CICS® job from a procedure by using the START command, or you can submit the CICS startup job stream through the internal reader.

About this task

For an example of a batch job that you can submit through the internal reader, see A sample CICS startup job. A sample CICS startup procedure gives an example of a cataloged procedure suitable for starting CICS as a started task.

When you run the startup job, you start a process called CICS system initialization. This process must finish before you run any transactions. Completion of CICS initialization is shown by the following message at the system console: 
DFHSI1517 - applid:  Control is being given to CICS.
CICS initialization involves many activities, some of which are:
  • Obtaining the required storage for CICS execution from the private area in the CICS address space, above and below the 16MB line.
  • Setting up CICS system parameters for the run, as specified by the system initialization parameters.
  • Loading and initializing the CICS domains according to the start option specified by the START= system initialization parameter.
  • Loading the CICS nucleus with the required CICS modules.
  • Installing CICS resource definitions by:
    • Loading, from the CSD, the groups of resources specified by the GRPLIST= system initialization parameter
    • Loading the control tables specified by system initialization parameters
  • Opening the data sets necessary for initialization, including any needed for backout if the previous run of your CICS region was not shut down normally. Data sets may also be opened for backout even after a successful shutdown, if they had suffered backout failures before the CICS shutdown, because failed backouts are retried at emergency restart.
  • Opening BSAM sequential devices as required in the terminal control table (TCT).

Also, if you are operating CICS with CICS recovery options, backout procedures may be used to restore recoverable resources to a logically consistent state. For example, backout can occur if you start CICS with START=AUTO and CICS detects that the previous shutdown was immediate or uncontrolled. With SDTRAN, an immediate shutdown does not always leave in-flight units of work to be backed out. Also, even if there were no in-flight UOWs, it is possible (although rare) that there were backout-failed UOWs for which backout will be retried.

For background information about backout, and recovery and restart, see Troubleshooting for recovery processing.

In the final stages of initialization, a set of programs can be executed as specified in a program list table (PLT). You specify the suffix of the PLT you want by means of the PLTPI parameter in the SIT. Initialization PLT programs run under control of a CICS task in CICS key. Their storage is in CICS-key storage, and protected from overwriting by other transactions.

The PLTPI resource managers start in the following sequence when specified in the system initialization table:

  1. CPSMCONN=CMAS
  2. CPSMCONN=LMAS
  3. CPSMCONN=WUI
  4. DBCTLCON=YES
  5. DB2CON=YES
  6. MQCON=YES

This sequence only applies to the above system initialization parameters and not for PLTPI programs in general.

For more information about the user ID under which PLT programs run, see PLT programs.

For programming information about writing PLT programs, see Writing initialization and shutdown programs.

If you are running CICS with DB2®, you can specify the DB2 subsystem ID to be used at PLT startup by the INITPARM system initialization parameter, as follows: 
INITPARM=(DFHD2INI='yyyy')
where yyyy is the 4-character DB2 subsystem ID. The value must conform to MVS™ JCL rules about special characters. You cannot use the ID of a data sharing group of DB2 subsystems on the INITPARM system initialization parameter — you must specify the ID of a single DB2 subsystem. If you want to use the INITPARM system initialization parameter to specify a DB2 subsystem, leave blank both the DB2GROUPID and the DB2ID in the installed DB2CONN definition. An ID specified in either of these attributes of the DB2CONN definition overrides an ID specified on the INITPARM system initialization parameter.