Enhanced checkpoint processing [CR 394506]

IQ 12.6 ESD #4.6 includes an enhancement to allow checkpoint processing to occur even when the database is experiencing a high rate of commits. The change allows fair access for checkpoints to occur in the presence of operations that suspend checkpoints such as commits. While it is still true that checkpoints, commits, and rollbacks are mutually exclusive, the change allows checkpoints to occur between commits and rollbacks, even when the database is experiencing a high commit rate.

Since checkpoints have opportunity to run more frequently in a high commit rate scenario, this reduces the number of transactions that checkpoint must apply at one time, thereby shortening the checkpoint time.This enhancement applies to both explicit checkpoints started by issuing a CHECKPOINT command and implicit checkpoints based on the -gc server start-up parameter or CHECKPOINT_TIME option setting. The new checkpoint behavior is automatically enabled when running 12.6 ESD #4.6 and is required.