Pathway/iTS System Management Manual (G06.24+)

Setting TMF Parameters
HP NonStop Pathway/iTS System Management Manual—426748-002
E-5
Precautions for Using TMF Parameters
operate on audited files require fewer checkpoints than SEND requests to servers
that do not operate under TMF protection.
TCP checkpointing requirements can be significantly reduced if Pathway applications
running with the TMF subsystem have TMF protected servers read outside of
transaction mode before updating the database.
You can improve the performance of a Pathway application by taking advantage of the
TCP checkpointing strategy for TMF protected servers, as follows:
•
Do not use transaction mode for a server with read-only access to a database if
the requester displays the data before any attempt is made to change the data. In
the event of a failure, the read operations are retryable and fault-tolerant operation
is maintained.
•
Do not use transaction mode for a server that writes to an entry-sequenced logging
file in which duplicates are acceptable. In the event of a failure, the requester can
retry the write operations, so there is no need to back out the write. In contrast, a
key-sequenced file requires a backout; otherwise, the transaction will fail when the
second write is attempted at the same location.
Precautions for Using TMF Parameters
If a TMF error occurs and makes normal operations impossible, setting the TMF
parameter options to OFF is not the solution for continuing normal operations. Setting
these options can have the following result:
•
A SCREEN COBOL program that uses ABORT-TRANSACTION or
RESTART-TRANSACTION to handle exceptions to normal program operation only
appears to execute; the TMF verbs have no effect.
•
With the SET SERVER TMF parameter defined as ON and the SET TERM TMF or
SET PROGRAM TMF parameters defined as OFF, the TCP makes checkpoint,
retry, and syncdepth decisions as if the TMF software were running. For example,
the TCP performs fewer checkpoints and opens servers with a sync depth of 0
instead of 1. In this case, the TCP is not running in fault-tolerant mode, and a
single CPU failure can cause the application to fail.
To determine how to address the TMF error, see the TMF Operations and Recovery
Guide.
Caution. If a SEND request outside of transaction mode is sent to a TMF protected server that
operates on nonaudited files, data might be lost because the TMF subsystem is not invoked
and the TCP performs fewer checkpoints.
Note. SERVER objects are created and controlled under TS/MP. For more information about
SERVER objects and the server environment, see the TS/MP System Management
Manualand the TS/MP Management Programming Manual.