CICS Reviewer Part 3

What are the CICS commands available for program control services?
1. LINK: To pass control to another program at the lower level, expecting to be returned.
2. XCTL: To pass control to another program at the same level, not expecting to be returned.
3. RETURN: To return to the next higher-level program or CICS.
4. LOAD: To load a program.
5. RELEASE: To release a program.

Explain the various ways data can be passed between CICS programs.
Data can be passed in three ways - COMMAREA, Transient Data Queue (TDQ) and Temporary Storage Queue (TSQ)

Data can be passed to a called program using the COMMAREA option of the LINK or XCTL command in a calling program. The called program may alter the data content of COMMAREA and the changes will be available to the calling program after the RETURN command is issued in the called program. This implies that the called program does not have to specify the COMMAREA option in the RETURN command.

If the COMMAREA is used in the calling program, the area must be defined in the Working Storage Section of the program (calling), whereas, in the called program, the area must be defined as the first area in the Linkage Section, using reserved name DFHCOMMAREA.

What are the differences between TSQ and TDQ?
Temporary Storage Queue names are dynamically defined in the application program, while TDQs must first be defined in the DCT (Destination Control Table). When a TDQ contains certain amount of records (Trigger level), a CICS transaction can be started automatically. This does not happen when using a TSQ. TDQ (extra partition) may be used by batch application; TSQ cannot be accessed in batch. The Transient Data Queue is actually a QSAM file. You may update an existing item in a TSQ. A record in a TDQ cannot be updated. Records in TSQ can be read randomly. The TDQ can be read only sequentially. Records in Temporary Storage can be read more than once, while records in Temporary Data Queues cannot, With TDQs it is a "one read" only.

Explain the basic difference between the Intra partition TDQ and Extra partition TDQ.
Intra Partition TDQs 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 TDQs is a group of sequential records which interfaces between the transactions of the CICS region and the system outside of CICS region. Each of these TDQs is a separate physical file, and it may be on the disk, tape, printer or plotter,

CICS Reviewer Part 4 is continued here.