Transient data queue
A CICS queue that is written and read in order, each item read only once, used for logs, printing and starting work in the background.
Also written TDQ, TD queue, WRITEQ TD, READQ TD, extrapartition, intrapartition, trigger level
A transient data queue, or TD queue, is a queue of items that are written and read in order. Unlike a temporary storage queue, reading an item removes it, so each item is read only once. Queues have four-character names and are defined as resources in CICS.
There are two kinds. An intrapartition queue lives inside CICS. It can have a trigger level: when that many items are waiting, CICS automatically starts a transaction to process them. That is a simple way to pass work to a background task. An extrapartition queue is connected to something outside CICS, usually a sequential dataset or SYSOUT. Writing to it is a way to produce a file or report that batch can read later.
Programs use EXEC CICS WRITEQ TD and READQ TD. CICS itself writes many of its own messages to TD queues, such as CSMT and CSSL, and these end up in the region's job output.
When you look for a CICS region's messages in SDSF, you are often reading the output of its extrapartition TD queues.
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- Temporary storage queueA named list of items a CICS program can write, read back and update, used to keep data between tasks.
- CICSThe transaction manager that runs online mainframe applications, and the software behind a great many screens bank staff use.
- EXEC CICSThe way a program asks CICS to do something, such as read a record, send a screen or call another program.
- CICS regionOne running copy of CICS, with its own programs, files and users. A site typically runs several.
- CICS transactionOne unit of online work in CICS: the whole exchange of receiving a request, doing the work, and sending a response.