SQL/MX 2.x Installation and Management Guide (G06.24+, H06.03+)

Planning Database Security and Recovery
HP NonStop SQL/MX Installation and Management Guide—523723-004
5-11
Levels of Database Recovery With TMF
Audited Files
Files protected by TMF are called audited files. All SQL/MX files (including files created
for tables) are audited by TMF, and changes to them are logged to audit trails.
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. You can configure an audit dump process for each audit
trail. You can reconfigure an audit dump process while TMF 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
TMF online dumps contain audited database files. If database files are damaged or
lost, you can avoid data loss by restoring the files from online dumps to disk, and then
applying audit trail images to reconstruct the files. Unlike backups, online dumps can
be made while transactions are being processed by database applications (that is,
while TMF is running, and are essential to most file recovery operations).
Levels of Database Recovery With TMF
TMF provides three mechanisms for database recovery:
•
Transaction Backout on page 5-11
•
Volume Recovery on page 5-12
•
File Recovery on page 5-12
The consistency of an SQL/MX database is ensured if a TMF recovery operation
completes without errors. TMF recovery methods protect both SQL/MX metadata and
SQL/MX 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