HP Integrity NonStop H-Series - Manual (Page 61)

Configuring Automatic Transaction Processing
HP NonStop AutoTMF Software User’s Guide—429952-013
4-17
Unilateral Aborts
NonStop AutoTMF software manages TFILE sharing effectively, using the TFILE to
support parallel and nowait automatic transactions, and to manage process
transactions. Your programs can use the TFILE in the conventional manner, but you
are bound by TMF limits on the number concurrent transactions in a single process
described below in
Number of concurrent transactions .
Unilateral Aborts
When a program updates audited files within a transaction, an external factor may
cause the transaction to be aborted and uncommitted updates to be rolled back. Such
aborts are called unilateral, because they do not require the cooperation of the process
that started the transaction. Factors causing unilateral aborts include:
•
A process is terminated by another process.
•
A server process that inherits a transaction process (or its CPU) fails before
replying to the transactional request.
•
A server process that inherits a transaction process performs an
ABORTRANSACTION request.
•
A CPU, a primary disk process, or a TMF component fails.
•
A transaction exceeds the system AutoAbort time limit.
•
The TMF operator aborts the transaction.
NonStop AutoTMF software prevents many sources of unilateral aborts and detects
and deals with unilateral aborts that are not preventable. When a unilateral abort does
occur, NonStop AutoTMF software achieves database consistency that is equivalent to
unaudited database consistency by:
•
Intercepting operations that would cause the process to terminate (such as ABEND
or STOP) and committing any outstanding automatic transaction.
•
Avoiding sending transactional requests to other processes so that those
processes cannot cause unilateral aborts.
•
Detecting unilateral aborts and abending the process. The program will not make
database updates that assume that earlier updates were completed.
•
Providing transaction isolation controls to prevent a unilateral abort from affecting
external users or database consistency; see the preceding subsection
Transaction
Isolation on page 4-7.
•
Providing an AUTOCOMMIT option that allows you to force all outstanding
automatic transactions to be committed before the process abends, to avoid
reaching the TMF AutoAbort time limit. See subsection
Forced Transaction Commit
below for details.
Unilateral aborts caused by hardware or system failures should be rare.