Defining The Database Backup Trigger - IBM E16RMLL-I - Tivoli Storage Manager Implementation Manual

Note: If you are changing the recovery log to rollforward mode, the recovery
log size must be increased. To estimate the new value, reset the cumulative
log consumption statistic using the administrative command reset
logconsumption. Monitor the cumulative consumption over a number of days.
Divide the cumulative consumption by the number of days since you reset the
value, to get an average value. A safe size for the log pool is around 30–40%
larger than this figure.

5.4 Defining the database backup trigger

The database backup trigger determines when to back up the Tivoli Storage
Manager database, based on the recovery log utilization. When the recovery log
is in rollforward mode, the potential for it to fill up is much greater than in normal
mode. If the recovery log fills up, it is possible that the server can stall or even
halt unexpectedly. By defining a database backup trigger, when the recovery log
usage reaches the defined percentage, the server database is automatically
backed up. The backup operation clears the cached transactions, clearing the
recovery log.
Use the define dbbackuptrigger command to define settings for the database
backup trigger, such as the percentage of the assigned capacity and device
class to be used for automatic database backups. You can also define the
number of incremental database backups that can be run before a full backup
must run. These settings are used only when the recovery log mode is
ROLLFORWARD.
The actual percentage to choose depends on the planning considerations
discussed in Chapter 2, "Implementation planning" on page 15. We recommend
using 75% as a starting point and use the default number of incrementals (six).
Monitor your environment's activity to make sure that you do not trigger database
backups too frequently, as this creates unnecessary load on the server and
increases tape mount activity. If database backups are triggering too frequently,
consider increasing the recovery log size.
Example 5-7 shows how to set the limit of 75% and run up to six incremental
database backups before a full database backup.
Example 5-7 Setting the database backup trigger
tsm: LOCHNESS_SERVER1>
numincremental=6 incrdevclass=lto2-dc
ANR2282I Database backup trigger defined and enabled.
tsm: LOCHNESS_SERVER1>
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IBM Tivoli Storage Manager Implementation Guide
def dbbackuptrigger devclass=lto2-dc logfullpct=75
query process