Pathway/iTS TCP and Terminal Programming Guide

Managing Transactions With the TMF Subsystem
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
5-2
TMF Application Structure
TMF Application Structure
This subsection describes the recommended structure for applications that use the TMF
subsystem.
One process (usually the SCREEN COBOL requester) coordinates all of the work
required to do a single TMF transaction; this process identifies the beginning and ending
points of each transaction. Additionally, if the server replies to a request message by
indicating that it failed to complete all of the changes, this process can either abort and
abandon the transaction or abort and retry the transaction according to the SCREEN
COBOL application.
The communication between requesters and servers is by standard interprocess I/O. The
SCREEN COBOL requester does the SEND operation, and the server does the
READUPDATE call for $RECEIVE and the REPLY call. Each request message and
the server’s reply to the message is for a single transaction.
Any disk I/O request is for a single transaction. The TMF subsystem appends the
process’s current transaction identifier to each disk-request message so that the audit
Figure 5-1. Pathway Application Programming for the TMF Subsystem
COBOL85, C,
C++, Pascal,
TAL, ...
TRANSID TRANSID
Audited
Database Files
Requester Server
SCREEN
COBOL
BEGIN- TRANSACTION
Request database
services
Abort and restart
transaction if necessary
ABORT- TRANSACTION
or
Process request by:
—Reading files
—Locking records
(following TMF
record-locking rules)
—Changing records
in files (changes are
associated with
TRANSID supplied
by requester)
—Aborting transaction
if necessary
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