A checkpoint is a point in time in the log when a known and consistent state for the database system is established.
A checkpoint can occur in one of these situations:
• When a DBSPACE is added. It’s a blocking checkpoint
• When resource limitations occur. For example, when physical log is 75% full
• Automatic checkpoints (AUTO_CKPTS)
Please note that the fast recovery depends on CKPTINTVL & RTO_SERVER_RESTART parameters.