Availability Guide for Application Design

Data Protection and Recovery
Availability Guide for Application Design—525637-004
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Online Dumps and Audit Dumps
Online Dumps and Audit Dumps
A combination of online dumps and audit dumps make file recovery possible in the
event of:
•
Corruption or loss of an audited data file due to an application error, operations
error, or a hardware failure while running a non-fault-tolerant configuration
•
Environmental catastrophe
•
Corruption of an audit-trail volume
An online dump provides a complete, historical view of a data file while continuing to
allow updates to the file and maintaining database consistency. System management
programs using the Subsystem Programmatic Interface (SPI) can be used to automate
the taking of these online dumps.
An audit dump involves making a backup copy of an audit-trail file. These audit-trail
files are used cyclically by the audit trail facility. When an audit-trail file is dumped, that
file becomes available for the audit trail to write new transaction audit records into. An
audit trail file is scheduled for dumping as soon as it is full. The file becomes available
for reuse when it has been dumped, it contains no active transactions, and no disk
volume needs the file for volume recovery.
An audit-trail file becomes a candidate for dumping when it contains no more active
transactions.
The audit dump can be made to tape or to disk. The tape or disk can be local or
remote. Remote dumping or remote storage of locally dumped tapes provides some
protection against environmental catastrophe.
File Recovery
File recovery protects your data from any situation from which volume recovery cannot
recover, for example, an environmental catastrophe or if an audited file or volume is
affected by the failure of a single disk volume or both disks of a mirrored volume.
File recovery starts by copying the last successful online dump back to the data file.
Changes made to the database since the last online dump are applied from the audit
trail. These audit-trail changes might all be on the audit-trail volume, or they might
need recovering from a recent audit-trail dump.
The speed with which TMF copies records from the audit trail to the volume restored
from the online dump is very fast. However, the total time for the file recovery operation
depends on how many audit dumps have been taken since the last online dump, and
on the size of those audit dumps.
APIs to Transaction Facilities
The programmatic interface to transaction control includes a procedure call or function
call to begin the transaction and a procedure call or function call to commit or abort the