Pathway/iTS TCP and Terminal Programming Guide

Managing Transactions With the TMF Subsystem
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
5-9
SET SERVER Command and the TMF Subsystem
•
How is TCP checkpointing strategy affected by the settings you specify for the TMF
parameter of the SET SERVER command?
•
What problems are caused by using the TMF OFF option of the SET TERM or SET
PROGRAM commands as a switch to turn TMF subsystem operation off for a
SCREEN COBOL requester that is communicating with servers running under the
TMF subsystem?
Understanding the answers to these questions ensures the consistency of the database
and helps you to improve the reliability and performance of the applications that use the
database.
SET SERVER Command and the TMF Subsystem
The SET SERVER command contains a TMF parameter with an ON or OFF option. By
setting this parameter you control how a TCP allows access to a server class, that is, the
types of operations a server class can perform.
•
TMF ON means the TCP allows a SEND operation to members of this server class
whether or not the SCREEN COBOL program is in transaction mode.
•
TMF OFF means the TCP allows a SEND operation to the members of this server
class only if the SCREEN COBOL program is not in transaction mode. OFF is the
default setting.
In addition, the TCP makes checkpointing decisions based in part upon the option
specified for the TMF parameter. You must match the TMF parameter setting to the
application environment. For further information, see TCP Checkpointing Strategy
on
page 5-12.
SET TERM and SET PROGRAM Commands and the TMF Subsystem
The SET TERM and SET PROGRAM commands each contain a TMF parameter with
an ON or OFF option.
•
TMF ON causes the TCP to invoke the corresponding Guardian procedure call for
any TMF statement issued from a SCREEN COBOL program. This setting allows
your SCREEN COBOL program to perform SEND operations to a server for which
the TMF parameter is set to ON. ON is the default setting whether or not the TMF
subsystem is running.
•
TMF OFF does not cause the TCP to invoke a corresponding Guardian procedure
call for any TMF statement issued from a SCREEN COBOL program. Instead, the
TMF statement appears (to the SCREEN COBOL program) to complete
successfully, and the program can continue to execute.
For most Pathway applications, you should use the default parameter settings, whether
or not the TMF subsystem is running.