TMF Planning and Configuration Guide (G06.24+)

Reconfiguring Audit Trails
HP NonStop TMF Planning and Configuration Guide—522416-004
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Changing the Overflow Threshold
they update in the database. Identify which volumes are generating the highest audit
rates and spread these volumes among the auxiliary audit trails.
To reassign a data volume to another audit trail in the configuration, you might first
need to configure an additional auxiliary audit trail. This requires you to first stop TMF,
delete the TMF configuration, and restart TMF. Then you must do the following:
•
Disable the volume (so that it is in the disabled clean state) by using a DISABLE
DATAVOLS command.
•
Delete it from the configuration by using a DELETE DATAVOLS command.
•
Add the volume again by using an ADD DATAVOLS command, specifying another
audit trail with a lower audit rate.
•
If you are doing file recovery, immediately perform an online dump.
Moving a data volume to another processor is a complex operation that involves
physically moving the device and making system configuration changes. If you need to
move a data volume to another processor, contact your service provider for assistance.
To protect your database, you must always disable the volume (so that it is in the
disabled clean state) before you move it.
Changing the Overflow Threshold
The overflow threshold specifies, as a percentage of overall audit-trail capacity, the
point at which TMF copies the earliest audit-trail file from an active-audit volume to an
overflow-audit volume. The default overflow threshold is 80%.
You can change the overflow threshold while transaction processing is in progress by
using the OVERFLOWTHRESHOLD parameter of the ALTER AUDITTRAIL command.
Increasing the overflow threshold means that the audit trail will fill to a higher level
before TMF copies the earliest audit-trail file to an overflow-audit volume. If you set the
overflow threshold too high, there could be an interruption of transaction processing as
TMF waits for space to become available on the active-audit volume. For example, if
the overflow threshold is set to 95% and the audit trail fills to that level, it is possible
that the remaining 5% will not be enough to hold the audit information generated while
files are being copied to the overflow-audit volume. This could result in the audit trail
reaching its begin-transaction-disable threshold, thereby preventing new transactions
from starting.
Decreasing the overflow threshold means that the audit trail will fill to a lower level
before TMF copies the earliest audit-trail file to an overflow-audit volume. If you set the
overflow threshold too low, the use of overflow-audit volumes could become
unacceptably high. TMF performance can be adversely affected when an excessive
number of files are copied from active-audit volumes to overflow-audit volumes.
Note. You should configure enough space on the active-audit volumes to accommodate the
maximum anticipated transaction activity. Overflow-audit volumes are intended to relieve disk
space pressure under exceptional circumstances.