A pool of checkpoint tasks works on the list of active databases in parallel. This pool is controlled by the configuration parameter number of checkpoint tasks. Where there is a checkpoint bottleneck, more checkpoint tasks translate to shorter recoverable logs, and recovery has less work to do in case of a failure, thus improving availability.
The default value of number of checkpoint tasks is 1, for serial checkpoints. The number of engines and number of open databases limit the value for this parameter. To facilitate parallel recovery, configure the maximum number of engines to be online at start-up. When you reduce the value for this parameter, checkpoints drain out, and when you increase the value, additional tasks are spawned.
Checkpoints are I/O-intensive; therefore, the effectiveness of parallel checkpoints is dependent on the layout of the databases and performance of the underlying I/O subsystem. Tune number of checkpoint tasks depending on the number of active databases and the ability of the I/O subsystem to handle writes.
See Chapter 5, “Setting Configuration Parameters,” in the System Administration Guide, Volume 1.
