CICS Frequently Asked Interview Questions and Answers

Aired Consulting 9/12/2009 No Comment

IBM CICS Frequently Asked Interview Questions.

Below are some important CICS Interview Questions.

What is MDT ?
Answer : Bit in the attribute byte indicating modification of field on screen.If the user keys in any data into the field, it turns the MDT ON indicating that the data is modified. To save transmission time , 3270 terminal sends a field over the TC line only if the MDT is on. Otherwise, the field value is not transmitted.

What is DFHCOMMAREA ?
Answer : DFHCOMMAREA in the Linkage section is used to pass the data in working storage commarea from one to program to another program. It should be defined with as at least one byte long. As the working storage section is freshly allocated for every execution.

What is Execution Interface Block (EIB) ?

Answer : EIB is a CICS area that contains information related to the current task, which can be used for debugging the program. The most widely used variables are EIBDATE, EIBTIME, EIBAID, EIBCALEN, EIBCPOSN, EIBRESP, EIBRSRCE (resource), EIBFN (recent CICS command code), EIBTRMID and EIBTRNID.

What are the important tables used in the CICS-DB2 environment ?

Answer : CICS manages it's communication with DB2 with special interface modules called CICS/DB2 Attachment Facility. When a CICS program issues a SQL statement, CICS requests the attachment facility to establish a connection with DB2 called a thread. The information about the CICS transaction and DB2 is entered in Resource Control Table (RCT). The plan information is referenced through the RCT Entries.

What are the various commands used to browse through a dataset ?

Answer : STARTBR, READNEXT, READPREV and RESETBR. The options used are DATASET, RIDFLD, RRN/RBA, GENERIC, and KEYLENGTH for the 3 commands, and INTO, LENGTH for READNEXT and READPREV command, and EQUAL/GTEQ for STARTBR only. RESP can be used with any. ENDBR is used to end the browse operation

What is 2 phase commit ?

Answer : It occurs when a programmer Issue's an Exec CICS Syncpoint command. This is called a two phase Commit because CICS will first commit changes to the resources under its control like VSAM files, before DB2 changes are committed. Usually CICS signals DB2 to complete the next phase and release all the locks.

What are ASRA,AICA,AEY9 abend ?

Answer : ASRA - Any data exception problem SOC7, SOC4 etc
AICA - Runaway Task.
AEY9 - DB2/IDMS Database is not up.

What are the differences between TSQ and a TDQ ?
Answer : 
(1) In Temporary Storage Queues Data is read randomly, While in Transient Data Queues data must be read sequentially.
(2) In a TSQ data can be read any number of times as it remains in the queue until the entire Queue is deleted. In TDQ data item can be read once only. To reuse the TDQ it must be closed and reopened.
(3) Data can be changed in TSQ, but not in TDQ.
(4) TSQ can be written to Auxiliary or Main Storage, while TDQ is written to Disk. Temporary storage is a holding place, while Transient data is always associated with destination. The
(5) TSQ name is defined dynamically, while a TDQ name need to be defined in the DCT. Note: An application uses TSQ 's to pass info' from task to task, while a TDQ to accumulate records before processing or send data for external use, such as a print operation or other.

What are Extra partition & Intra partition TDQs ?

Answer : Extra-partition TDQ's are datasets used for communication between CICS and other CICS/Batch regions. Intra-partition TDQ's are queues for communication within CICS region. CICS stores the Intra-partition TDQ in a dataset 'DFHNTRA' on the Disk. Extra-partition TDQ doesn't have to be a disk file, it can reside on any device that's a valid QSAM/VSAM. The DCT entry contains the destination-Id, type of TDQ, Destination, Trigger level if needed

How is an Abend handled in a CICS program ?

Answer : The HANDLE ABEND command is used to trap and Handle errors. It has 4 possible options and only one of them can be used with this command at a time. The options are Program(...) to transfer control to the program, Label(...) to transfer control to the specified paragraph, Cancel option keeps the earlier Handle Abends from being executed. Reset option will reactivate the Handle Abend commands, which were previously cancelled.

What is Quasi-reentrancy ?

Answer : There are times when many users are concurrently using the same program, this is what we call Multi-Threading. For example, 50 users are using program A, CICS will provide 50 Working storage for that program but one Procedure Division. And this technique is known as quasi-re-entrancy.
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