Pathway/iTS TCP and Terminal Programming Guide

Managing Transactions With the TMF Subsystem
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
5-4
SCREEN COBOL Verbs for the TMF Subsystem
When END-TRANSACTION or ABORT-TRANSACTION is executed, the transaction
identifier is discarded and can no longer be used.
For the PATHCOM or SPI SUSPEND, STOP, or FREEZE commands, the effect of
operating in transaction mode is like setting the STOP-MODE special register to a
nonzero value; none of these commands can take effect until the terminal leaves
transaction mode and the terminal STOP-MODE register is 0.
The SUSPEND! and FREEZE! commands take effect immediately and cause
transaction backout.
The ABORT command takes effect immediately. If the terminal is in transaction mode
when this command is executed, the transaction is aborted.
For details regarding SUSPEND, FREEZE, STOP, and ABORT, refer to the NonStop™
TS/MP System Management Manual and the Compaq NonStop™ Pathway/iTS System
Management Manual.
SCREEN COBOL Verbs for the TMF Subsystem
In a SCREEN COBOL requester, you invoke the functions of the TMF subsystem by
using the following transaction-control statements:
•
ABORT-TRANSACTION aborts and backs out a transaction.
•
BEGIN-TRANSACTION begins a transaction.
•
END-TRANSACTION ends a transaction.
•
RESTART-TRANSACTION backs out a transaction and then starts it from the
BEGIN-TRANSACTION point with a new transaction identifier.
When you use these transaction statements in your SCREEN COBOL programs,
Pathway/iTS handles a number of failure cases itself by automatically aborting the
transaction and restarting it at the BEGIN-TRANSACTION point. The TCP does the
following:
•
Takes care of all details involved in handling concurrent active transactions
•
Keeps track of the transaction identifiers for multiple transactions
•
Checkpoints the transaction identifier
•
Operates as a fault-tolerant process pair
•
Handles the TMF programming involved when the backup process takes over
Note. To work appropriately with the ORDERLY option of the PATHCOM SHUTDOWN2
command, SEND requests must be coded so that a terminal can be stopped after the last I/O
operation in the logical transaction completes. In other words, the requester must end or abort
the current transaction after the last SEND request in the transaction, based on the server’s
reply to the SEND request. For details regarding the SHUTDOWN2 command, refer to the
NonStop™ TS/MP System Management Manual.