Can anyone explain cics initiation process

karthi_ind · Posted: Sun Jun 06, 2004 3:10 pm

hi

can anyone explain cics initiation process ?
i need explanation for all tables.

anbudan
karthi G.

Venku · Posted: Wed Jun 09, 2004 12:31 pm

CICS initialization job is a JCL available to systems CICS systems programmers. Initially it loads all the libraries associated with your installation like CICS support libraries, Support to CICS EXECS, CPSM, DB2, MQSERIES, TCP SOCKETS, LANG ENV, and DEBUG TOOLS. Also loads all the load modules associated with programs. It also loads all the required CICS run time datasets. Initialization job varies from installation to installation. The CICS load library that the application programmers place the program load modules should be added to the order of concatenation in the STEPLIB DD statement of the CICS initialization job.

If you want to take a look try SYS1.PROCLIB and the member name should start with CICS* though it varies from each mainframe shop. Here I maintain these and naming standard starts with CICS.

karthi_ind · Posted: Mon Jun 14, 2004 3:18 pm

meetsrk · New User Joined: 13 Jun 2004 Posts: 85

hi karthik_ind,

in cics, when u type a transaction id., it finds from which terminal u typed using terminal control table i.e TCT later it allocates the storage using SCT for that terminal.

then using the transaction id., it checks for the program name in the program control table (PCT), in PCT it has the program name. then using that program name it finds the load module address in PPT. and finally loads that program.

i hope the above is correct.
if not i will give later the correct explanation.
bye
meetsrk

Johore · Specialist Joined: 12 Sep 2003 Posts: 19

(A) TERMINAL CONTROL PROGRAM (TCP) IS MONITORING THE TERMINAL NETWORK(POLLING) ASSIGNED TO CICS REGION TO SEE WHICH TERMINAL IS READY TO TRANSMIT A MESSAGE(ENTER A TRANSID).

(B) IF TCP FINDS SUCH A MESSAGE IT WILL SEARCH THE TCT TO FIND OUT WHETHER A CICS APPLICATION MODULE (PROGRAM) IS CURRENTLY IN THE CORE WAITING FOR THE RESPONSE FROM THAT TERMINAL. IF NOT WAITING THEN TCP CONSIDERS IT AN INITIATION OF A NEW TASK. THEN TCP CREATES TIOA AREA AND SCP (STORAGE CONTROL PROGRAM) WILL RECEIVE CONTROL AND INITIATES STORAGE FOR PROGRAM TO BE EXECUTED. IN EITHER CASE, WAITING FOR RESPONSE OR INITIATION OF AN NEW TASK, THE TCP PASSES CONTROL TO THE TASK CONTROL PROGRAM (KCP) WITH THE NAME OF THE
TRANSID ENTERED.

(C) THE TASK CONTROL PROGRAM TAKES THAT TRANSID AND COMPARES IT TO THE ENTRIES IN THE PROGRAM CONTROL TABLE (PCT) TO VALIDATE THE TRANSID AND FIND OUT THE CORRESPONDING APPLICATION MODULE RESPONSIBLE FOR THE TRANSACTION. IF VALIDATION OF THE TRANSID FAILS CONTROL IS RETURNED BACK TO THE TCP WHICH IN TURN SENDS THE FOLLOWING MESSAGE TO THE SCREEN:'INVALID TRANS-ID. PLEASE RE-ENTER' IF VALIDATION OF THE TRANSID IS SUCCESSFUL THE KCP WILL PASS CONTROL TO THE PROGRAM CONTROL PROGRAM (PCP) TOGETHER WITH THE NAME OF THE CICS APPLICATION MODULE(PROGRAM NAME) RESPONSIBLE FOR THAT TRANSACTION.

(D) THE PROGRAM CONTROL PROGRAM TAKES THE NAME OF THE APPLICATION MODULE AND COMPARES IT TO THE ENTRIES IN THE PROGRAM PROCESSING TABLE(PPT) TO FIND A MATCH FOR THE APPLICATION MODULE AND WHETHER ITS RESIDING IN THE CORE MEMORY OR IN AUXILLARY STORAGE. THIS IS ACHIEVED BY CHECKING THE USAGE COUNTER FIELD IN THE PPT TABLE. THE VALUE OF THE USAGE COUNTER FIELD IS EQUAL TO THE NUMBER OF TASKS CURRENTLY USING THIS APPLICATION MODULE. IF USAGE COUNTER IS EQUAL TO ZERO CICS WILL HAVE TO LOAD THE APPLICTION MODULE INTO CORE MEMORY FROM CICS LOAD LIBRARY DEFINED IN CICS STARTUP PROCEDURE. IN EITHER CASE, IF USAGE COUNTER IS GREATER THAN ZERO AND APPLICATION MODULE EXISTS IN CORE MEMORY, OR HAD TO BE LOADED FROM THE LOAD LIBRARY
CONTROL WILL NOW BE PASSED TO THE APPLICATION MODULE.

gowtham_srgp · New User Joined: 09 Jun 2005 Posts: 38