Incremental Checkpoints

Question

What is incremental Checkpoints? how it differs from normal checkpoints?

Answer 1

Checkpointing is the act of flushing the dirty buffers from the cache. This is basically done to make sure that in the case of instance crash,Oracle should be able to recover theinstance with minimum dirty buffers. Now , as the cache being quite large, if the whole cache has to be recovered, it will take a huge time. Thus, there is a periodic flush of it which is controllable by manuall. This kind of checkpointing is called Incremental checkpointing. The incremental checkpointing is basically the information of the most oldest dirty buffer's address(RBA) which is recorded in the control file so that it knows that in order of a crash,from where it has to start the recovery. This list of dirty buffers is maintained in the checkpoint queue which is one per workarea within the buffer cache.

In incremental checkpoint process, CKPT process records lowest Low RBA to the control file to keep advancing the Buffer checkpoint Queue (BCQ) to make easy and fastest Active Checkpoint Queue (ACQ).