Database Replication and Clustering
The frequency of extractions by the CDC extraction mechanism can be
controlled by using the
maxSleepTime parameter,
which controls the maximum sleep time between data checks within the CDC
tables. By default, the replicator checks for changes every second.
If there are no changes, the sleep time before the next query is increased
by the sleepAddition
until the value reaches, or is above, the
maxSleepTime parameter.
When changes are identified, the sleep time is reset back to 1 second. For
example:
Increasing maxSleepTime
sets the maximum sleep time and can help to reduce the overall redo log
content generated, which in turn reduces the amount of disk space required
to store and generate the log content.The value can be set during
installation with tpm using:
shell> tpm update alpha --property=replicator.extractor.dbms.maxSleepTime=32 ...
The minimum sleep time can be configured to set the minimum sleep time
between checks of the CDC table using the
minSleepTime. This
reduces the size of the redo log, at the expense of lowering the frequency
of updates from the CDC into THL. For example, setting a minimum of 16
seconds would change the sample interval shown in the previous table to:
An additional parameter,
sleepAddition, defines
the increment value added to the
minSleepTime parameter at
each call until
maxSleepTime is reached.
For example, a setting of 8s would generate a table as follows: