AutoTMF Software User's Guide (Update 15)

Configuring Automatic Transaction Processing

HP NonStop AutoTMF Software User’s Guide—429952-017

4-6

Transaction Commit

To commit an automatic transaction, AutoTMF 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 AutoTMF ensures that normal, unaudited,

file-locking behavior and record-locking behavior are observed.

AutoTMF ensures that the database does not become inconsistent by preventing the

premature unlocking of files and records. When the application process has logically

unlocked records and files, AutoTMF can safely commit automatic transactions. If the

process is still holding locks, automatic transactions are not committed and remain

active until the process releases the locks.

Automatic transactions are committed according to a proprietary set of processing

rules, driven by the following activities and events:



Process operations that lock, update, and unlock files and records; such

information determines both the lock protocols that need to be preserved and the

actual lock state of open files.



Process operations that signal a requirement or an opportunity to commit an

automatic transaction. For example, when a server process replies to a requestor:

the server has performed database operations for one request and will await a new

request; any outstanding automatic transaction should be committed at this point.



Process operations, such as termination, that would cause automatic transactions

to be aborted.



Process operations that may require a commit to isolate automatic transactions

from external effects, as described in Transaction Isolation on page 4-7



Time that an automatic transaction has been alive; you can configure the maximum

transaction lifetime to a reasonable interval that is consistent with good

performance



Amount of update activity performed under an automatic transaction; you can

configure the maximum number of updates in a transaction to keep the transaction

overhead to a reasonable fraction of the total processing cost.

Transactions that are used for a large number of updates accumulate locks, cause

other resource problems, and have a larger impact if aborted unilaterally.

Transactions tend to increase the time during which locks are held and this increased

time may result in increased lock contention. This phenomenon is common in all

transaction-based database systems. Lock contention can be monitored by using the

NonStop AutoTMF LISTLOCKS command.