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.

"Intrapartition" refers to data on direct-access storage devices for use with one or more programs running as separate tasks. Data directed to or from these internal queues is referred to as intrapartition data; it must consist of variable-length records. All intrapartition transient data destinations are held as queues in the same VSAM data set, which is managed by CICS. An intrapartition destination requires a resource definition containing information that locates the queue in the intrapartition data set. Intrapartition queues can be associated with either a terminal or an output data set. When data is written to the queue by a user task, the queue can be used subsequently as input data by other tasks within the CICS region. All access is sequential, governed by read and write pointers. Once a record has been read, it cannot be read subsequently by another task. Intrapartition data may ultimately be transmitted upon request to the terminal or retrieved sequentially from the output data set.

Typical uses of intrapartition data include:

* Message switching
* Broadcasting
* Database access
* Routing of output to several terminals (for example, for order distribution)
* Queuing of data (for example, for assignment of order numbers or priority by arrival)
* Data collection (for example, for batched input from 2780 Data Transmission Terminals)


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.


Extrapartition queues (data sets) reside on any sequential device (DASD, tape, printer, and so on) that are accessible by programs outside (or within) the CICS® region. In general, sequential extrapartition queues are used for storing and retrieving data outside the CICS region. For example, one task may read data from a remote terminal, edit the data, and write the results to a data set for subsequent processing in another region. Logging data, statistics, and transaction error messages are examples of data that can be written to extrapartition queues. In general, extrapartition data created by CICS is intended for subsequent batched input to non-CICS programs. Data can also be routed to an output device such as a printer.

Data directed to or from an external destination is referred to as extrapartition data and consists of sequential records that are fixed-length or variable-length, blocked or unblocked. The record format for an extrapartition destination must be defined in a TDQUEUE resource definition by the system programmer.


Note: If you create a data set definition for the extrapartition queue using JCL, the DD statement for the data set should not include the FREE=CLOSE operand. If FREE=CLOSE is specified, attempts to read the queue after the queue has been closed and then re-opened can receive an IOERR condition.