HP Integrity NonStop H-Series - Manual (Page 50)

Configuring Automatic Transaction Processing
HP NonStop AutoTMF Software User’s Guide—429952-013
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Transaction Creation
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avoid long-running transactions in programs that have unusual locking behavior.
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force a single-transaction-per-update. Note that you also must specify
MAXUPDATES 1 to force single-transaction-per-update. Each file configured
through SEPARATETX and MAXUPDATES 1 uses its own separate transaction
that is committed immediately after an update.
Other options you can configure for a separate transaction are NOWAIT,
AUTOCOMMIT and MAXTIME.
A process may have both common and separate automatic transactions; all automatic
transactions in a process are managed independently.
Transaction Creation
Automatic transactions are created on demand, whenever a process accesses an
audited file and the process state and the NonStop AutoTMF configuration indicates
that the access requires an automatic transaction.
Typically, an automatic transaction is created if a process accesses an audited file for a
locking operation or an update operation, and that process does not have its own
transaction. You can configure certain files for automatic transactions, either common
or separate, regardless of the process transaction. You can also configure files that
should not be accessed through an automatic transaction.
The first transactional access on a file OPEN determines if operations on that OPEN
should use automatic transactions. Automatic transactions are used consistently, even
if the program handles transactions inconsistently.
Transaction Commit
To commit an automatic transaction, NonStop AutoTMF software analyzes all file-
access operations. File locking, record locking, and update operations are the primary
factors that determine when automatic transactions may be committed.
Unaudited file-locking behavior and record-locking cannot be replicated when
performing operations on audited files, but NonStop AutoTMF software ensures that
normal, unaudited, file-locking behavior and record-locking behavior are observed.
NonStop AutoTMF software ensures that the database does not become inconsistent
by preventing the premature unlocking of files and records. When the application has
logically unlocked records and files, NonStop AutoTMF software can safely commit
automatic transactions.
Note. Do not configure files that were previously audited (the application programs already
access them under their own transaction) as SEPARATETX. This can lead to locking problems.