Explanation/Reference:
Explanation:

Checkpoint Process (CKPT)
A checkpoint is a data structure that defines a system change number (SCN) in the redo thread of a database. Checkpoints are recorded in the control file and in each data file header. They are a crucia element of recovery.
When a checkpoint occurs, Oracle Database must update the headers of all data files to record the details of the checkpoint. This is done by the CKPT process. The CKPT process does not write blocks to disk; DBWw always performs that work. The SCNs recorded in the file headers guarantee that all changes made to database blocks prior to that SCN have been written to disk.
The statistic DDWR checkpoints displayed by the SYSTEM_STATISTICS monitor in Oracle Enterprise Manager indicate the number of checkpoint requests that have completed.