TMF Introduction (G06.26+)

TMF Overview

HP NonStop TMF Introduction—522414-002

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Database Recovery

Log of Updates in Audit Trails

An audit trail, sometimes called a “transaction log,” is a series of files in which TMF

records information about a transaction’s changes to a database.

An audit trail contains audit records. Audit records contain information about each

transaction, such as the final outcome of transaction commit or abort operations, as

well as before-images and after-images of all data records changed by each

transaction.

•

Before-images are copied portions of the data records before the transaction

changed them; they are used to back out a transaction.

•

After-images are copied portions of the changed records; they are used in volume

recovery and file recovery.

The files or tables protected by TMF are called audited files. Only audited files have

change records logged to audit trails. Files that are not protected by TMF are

nonaudited files and do not have changes logged. Site personnel can choose which

files are to be audited on a file-by-file basis, depending on application requirements.

The relationship of an audit trail to audited database files is shown in Figure 1-7.

Figure 1-7. The Audit Trail and Audited Database Files

Audited Files

Audit Trail

(Before-images and

After-images) and

Control Records

Server

UPDATES

VST040.vsd

Non-Audited File

$AUDIT

$DB