Which two statements are true about checkpointing（）

• A、The checkpoint frequency decreases with the smaller redo log file size.
• B、It ensures that all committed data is written to the data files during normal shutdown.
• C、The frequent full checkpoint in a database can cause the overall degradation of the database performance.
• D、It prompts the Checkpoint （CKPT） process to write data to the data files and redo information to the online redo log files.