TMF Introduction (G06.26+)

Transaction Protection and Database Recovery

HP NonStop TMF Introduction—522414-002

3-3

Master Audit Trail

The master audit trail (MAT) contains TMF control information, such as commit or abort

records for each transaction, and information describing the logical ordering of audit

information in all audit trails in the system. The master audit trail can also store audit

information generated by a set of audited volumes. There must be exactly one master

audit trail in a TMF system. The master audit trail is named MAT.

Auxiliary Audit Trail

Auxiliary audit trails receive the audit information generated by a specified set of

audited volumes; they do not contain TMF control information. Although most

environments require only a master audit trail, each TMF system can have up to 15

auxiliary audit trails. Auxiliary audit trails can be used to increase overall auditing

capacity and throughput, or to logically separate operations related to sets of audited

volumes. Auxiliary audit trails are named AUXnn (nn is a two-digit value ranging from

01 to 15).

Audit-Trail Files and Rollover

TMF preallocates audit-trail files to ensure that disk space is available for these files as

it is needed. Audit-trail files are named in sequence on each audit volume, enabling

TMF to keep track of which audit-trail files are most recent and which are oldest.

TMF requires at least two available audit-trail files whenever audit records need to be

written. One is the audit-trail file to which TMF is currently writing; the other file is held

in reserve to be used when the current audit-trail file becomes full. This requirement is

so important that there is a special TMF mechanism for managing the audit-trail files:

audit-trail rollover ensures audit-trail availability, allowing uninterrupted execution of all

applications.

Rollover involves renaming: just before the current audit-trail file becomes full, TMF

renames an audit-trail file to become the new highest-numbered file in the sequence,

and resets the new file’s end-of-file pointer to 0. Then, when the current audit-trail file

is filled, TMF can proceed to the next file and continue writing audit information

uninterrupted. Renaming an existing file takes considerably less time than creating a

completely new file.

Figure 3-2 illustrates audit-trail rollover. The current audit-trail file is AA000006; the

rollover mechanism has already renamed an old file to AA000007 and reset its end-of-

file pointer to 0. When AA000006 is full, TMF begins writing audit information to

AA000007 and rollover occurs: AA000005 is then renamed to AA000008, and its end-

of-file pointer is reset to 0.