SQL/MP Installation and Management Guide

Planning Database Security and Recovery
HP NonStop SQL/MP Installation and Management Guide—523353-004
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Levels of Database Recovery
Audited Files
Files or tables protected by the TMF subsystem are called audited files. Only audited
files have changes logged to audit trails. Files not protected by the TMF subsystem are
nonaudited files and do not have changes logged. You can choose which files are to
be audited on a file-by-file basis, depending on application requirements. Only files on
a TMF-configured data volume can be audited.
Audit Dumps
An audit dump is a copy of an audit trail file written to a tape or disk volume by an audit
dump process. If audit dumping is configured, audit dumps occur automatically when
an audit trail file becomes full. An audit dump process can be configured for each audit
trail; it can be reconfigured while the TMF subsystem is running. Audit dumps are used
by the file recovery process; they remain either on audit-restore volumes or on the
audit dump medium (disk or tape) until they are no longer needed for recovery.
Online Dumps
An online dump is a copy of an audited database file written to tape or disk in case of
media failure or other damage to a database such as an accidental purge operation.
Each online dump of a file provides an image of a file that can be used by the file
recovery process to reconstruct the file. Thus, online dumps are essential for most file
recovery operations.
An online dump is created when a TMF DUMP FILES command is issued. Online
dumps can be made while transactions are being processed by database applications.
Levels of Database Recovery
The TMF subsystem provides three mechanisms for database recovery: transaction
backout, volume recovery, and file recovery.
The consistency of an SQL database is ensured if any TMF recovery operation
completes without errors. TMF recovery methods protect both SQL catalog tables and
audited SQL objects.
Transaction Backout
Transaction backout provides automatic online recovery for aborted transactions. A
transaction is aborted when an event prevents the transaction from being committed.
Possible events include:
•
Program suspension or abnormal termination because of an error or specific
programmatic request
•
Processor failure
•
Communication failure between participating nodes of a network-distributed
transaction