Understanding CICS terminology

Familiarize yourself with terms that have special meanings in CICS®.
Transaction
A unit of processing, consisting of one or more programs.
Task
The processing of a transaction for a program user.
Conversational
The CICS term for running a program in nonsegmented mode. A conversational program consists of a sequence of alternating entries and responses between a user and the program. File and database position and locks, and storage resources are held across the terminal I/O operation.
Pseudoconversational
The CICS term for running a program in segmented mode. A pseudoconversational program consists of a series of single CICS tasks designed to appear to the user as a continuous conversation. File and database position and locks, and storage resources are released across the terminal I/O operation. The program must save conversation status before terminal output and restore it on terminal input.
Communication area (COMMAREA)
A data area used to transfer information between two programs within a transaction or between two transactions from the same terminal. When one program transfers to another, the COMMAREA can be any data area the transferring program can access. The transferred-from program can both pass data to that area and receive results in the area. The data area is usually the working storage area of that program.
Transaction Work Area (TWA)
A fixed length storage area allocated for each transaction task control area. Generated EGL programs use a 1024 byte section of the TWA. The offset of the EGL section of bytes is controlled by the twaOffset build descriptor option.
Resource Definitions Online (RDO)
Definitions of resources used or managed by the CICS system. Each definition is created by using resource definition online (RDO). The following list shows the types of definitions:
TDQUEUE
Used to define transient data destinations for the system.
FILE
Used to define files used by the system.
PROGRAM
Contains information about each program. The Rational® COBOL Runtime for z/Series programs, generated COBOL programs, libraries, and servers, FormGroup online print services programs, FormGroup format modules, and DataTables must be defined. Alternatively, if you use the CICS autoinstall feature for programs you do not need to create PROGRAM definitions.
TRANSACTION
Defines the transaction identifiers that can be entered by program users. For each transaction, it also defines the related program that starts the processing for the transaction.
DB2CONN, DB2ENTRY, and DB2TRAN
Describe the interface between the CICS region and DB2®, including the association of transaction codes with DB2 program plans.
PROFILE, TYPETERM, and TERMINAL
Contain descriptions of terminals, their features, and operating information.
Temporary storage queue
A CICS managed file for storing intermediate results. Records in a temporary storage queue can be accessed serially or by a relative record number. Descriptions of the two types of temporary storage follow:
Auxiliary
A temporary storage queue that is stored on DASD. It can be recovered and maintained from one CICS run to the next.
Main
A temporary storage queue that exists in the CICS address space. It is not recoverable and is not maintained from one CICS run to the next.
Transient data queue
A CICS managed file that is serially organized. Descriptions of the two types of transient data queues follow:
Extrapartition transient data queue
A CICS managed serial file in a system sequential data set or tape. The file can be an input file or an output file but not both. Extrapartition queues are not recoverable.
Intrapartition transient data queue
A transient data queue that is accessible to transactions running in a CICS region. The queue can be used for both input and output. On z/OS®, the queue is stored in a VSAM entry sequenced data set. Intrapartition queues can be recovered.

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