TMF Planning and Configuration Guide (H06.06+, J06.03+)

Reconfiguring Audit Trails

HP NonStop TMF Planning and Configuration Guide—540136-005

3-9

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.

Changing the Begin-Transaction-Disable

Threshold

The begin-transaction-disable threshold specifies, as a percentage of overall audit-trail

capacity, the point at which TMF prevents any new transactions from starting. The

default begin-transaction-disable threshold is 90%.

You can change the begin-transaction-disable threshold while transaction processing is

in progress by using the BEGINTRANSDISABLE parameter of the ALTER

AUDITTRAIL command.

Increasing the begin-transaction-disable threshold means that the audit trail fills to a

higher level before TMF prevents new transactions from starting. If you set the begin-

transaction-disable threshold too high, audited activity could cease until space

becomes available on the audit-trail volumes. In that situation, requests to data

volumes might be suspended, or data volumes might start going down, thus preventing

access to the audited database tables and files. Before increasing this threshold,

consider increasing the size of the audit trail.

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.