CICS Interview Questions and Answers - DoAnswers.com

(Customer Information Control System) A TP monitor from IBM that was originally developed to provide transaction processing for IBM mainframes. It controls the interaction between applications and users and lets programmers develop screen displays without detailed knowledge of the terminals used. It provides terminal routing, password security, transaction logging for error recovery and activity journals for performance analysis. CICS is a transaction processing system that can handle both small and large numbers of transactions, although it is designed mainly for huge numbers. The top transaction number so far recorded is in the several thousands per second. The functionality extends from traditional mainframes to online batch activity as well. CICS has also been made available on non-mainframe platforms including the RS/6000, AS/400 and OS/2-based PCs.CICS commands are written along with and into the source code of the applications, typically COBOL, although assembly language, PL/I and RPG are also used. CICS implements SNA layers 4, 5 and 6.

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Reentrant program is a program which does not modify itself so that it can reenter to itself and continue processing after an interruption by the operating system which, during the interruption, executes other OS tasks including OS tasks of the same program. It is also called a "reenterable" program or"serially reusable" program.

A quasi-reentrant program is a reentrant program under the CICS environment. That is, the quasi-reentrant program is a CICS program which does not modify itself. That way it can reenter to itself and continue processing after an interruption by CICS which, during the interruption, executes other tasks including CICS tasks of the same program.

In order to maintain the quasi-reentrancy, a CICS application program must follow the following convention: Constants in Working Storage: The quasi-reentrant program defines only constants in its ordinary data area (e.g. working Storage Section ).

These constants will never be modified and shared by the tasks. Variable in Dynamic Working Storage: The quasi reentrant program acquires a unique storage area ( called Dynamic Working Storage --DWS) dynamically for each task by issuing the CICS macro equivalent GETMAIN. All variables will be placed in this DWS for each task.

All counters would have to be initialized after the DWS has been acquired. Restriction on Program Alteration: The program must not alter the program itself. If it alters a CICS macro or command, it must restore the alteration before the subsequent CICS macro or command.

32. Explain the basic difference between Intra partition TDQ and Extra partition TDQ.

INTRA PARTITION TD QUEUEs It is a group of sequential records which are produced by the same and / or different transactions within a CICS region. These Qs are stored in only one physical file ( VSAM ) in a CICS region, which is prepared by the system programmer.

Once a record is read from a queue, the record will be logically removed from the queue; that is the record cannot be read again. EXTRA PARTITION TD QUEUEs It is a group of sequential records which interfaces between the transactions of the CICS region and the systems outside of CICS region. Each of these TDQs is a separate physical file, and it may be on the disk, tape, printer or plotter.

33. Explain the difference among the EXEC LINK, EXEC XCTL and Cobol II static call statements in CICS.

COBOL II allows for static calls which are more efficient than the LINK instruction which establishes a new run- unit.

34. Explain the means of supporting pseudo conversation programming. (E.g. Storing and restoring of states, control flow, error handling)

we send a map using SEND MAP command. Immediately we release the program by using EXEC CICS RETURN command. In this command we mention the TRANSACTION ID which is to be executed after receiving the map. In this command we also specify the data that should be stored in COMMUNICATION AREA for later use.

When this command is executed the corresponding program is released from the memory. After receiving the response from the terminal the program is again loaded and this time the data which we stored in communication area will be copied into the working storage section. And the map will be received with RECEIVE MAP command.

The variable EIBCALEN in EIB holds the length of communication area. In procedure division we checks the value of EIBCALEN If it is zero, we first send the map followed by RETURN command. Otherwise, that is if EIBCALEN is not zero, we know that this transaction is not running first time and we receive the map by using RECEIVE MAP command.

MRO is the mechanism by which different CICS address spaces with in the same CPU can communicate and share resources.

Function request shipping is one of the CICS modes of intercommunication which allows an application program in a local CICS to access resources owned by a remote CICS.

Transaction routing is a CICS mode of intercommunication which allows a terminal connected to local CICS to execute another transaction owned by a remote CICS.

39. For multithreading an application program need not be re-entrant(True or False).

40. For protecting a transaction using the transaction security function, the two things that must be done are: 1. in the SNT entry of the user who you which to allow to access a protected transaction, specify SCTKEY=n 2. In the PCT entry of the transactions