Message processing with IMS TM

IMS Transaction Manager application programs can be written in assembler language, C language, COBOL, Pascal, and PL/I to process messages.

How your program processes messages
To retrieve and send messages, an IMS TM application program issues calls to IMS TM. When your program issues a call to retrieve a message, IMS TM places the input message in the I/O area you name in the call. Before you issue a call to send a message, you must build the output message in an I/O area in your program.
How IMS TM edits messages
When an application program passes messages to and from a terminal, IMS TM edits the messages before the program receives the message from the terminal and before the terminal receives the message from the application program.
Message processing considerations for DB2
For the most part, the message processing function of a dependent region that accesses DB2® databases is similar to that of a dependent region that accesses only DL/I databases.
Sending messages to other terminals and programs
When an application program processes a message from a terminal, it usually sends the response to the terminal that sent the input message. But sometimes you might want to send output messages to a terminal other than the originating terminal, or to other terminals in addition to the originating terminal. You might also want to send messages to other application programs.
Communicating with other IMS TM systems using Multiple Systems Coupling
In addition to communicating with programs and terminals in your IMS TM system, your program can communicate with terminals and programs in other IMS TM systems through Multiple Systems Coupling (MSC).
IMS conversational processing
You can write conversational programs to perform conversational processing with IMS Transaction Manager.
Processing conversations with APPC
APPC/IMS supports standard, modified, and CPI Communications driven application programs.
Processing conversations with OTMA
You can run IMS conversational transactions through OTMA.
Backing out to a prior commit point: ROLL, ROLB, and ROLS calls
When a program determines that some of its processing is invalid, you can use these calls to remove the effects of its incorrect processing: Roll Back calls ROLL, ROLS using a database PCB, ROLS with no I/O area or token, and ROLB.
Backing out to an intermediate backout point: SETS/SETU and ROLS
You can use a ROLS call either to back out to an intermediate backout point established by a prior SETS or SETU call or to back out to the prior commit point.
Writing message-driven programs
A message-driven program is similar to an MPP: it retrieves messages and processes them, and it can read and update MSDBs, DEDBs, and full-function databases.
Coding DC calls and data areas
The way you code DC calls and data areas depends on the application programming language you use.

Parent topic: Application programming for IMS TM