Which two statements are true about checkpointing? (Choose two.)
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.
A. When the case of the redo log file is too small , frequent switching will log information is written to the checkpoint frequency data files will increase rather than decrease . A wrong .
B. In the normal closed libraries and will generate a full checkpoint , CKPT process will make DBWn data files are written to all that have been submitted , B pairs.
C. frequent occurrence of checkpoints will increase I / O read and write times , resulting in a decline in database performance , so the C pair.
D.CKPT redo information is written to the redo logs , DBWn data is written into the data file instead CKPT.D wrong .
Every three seconds ( or more frequently ), CKPT process once the data is stored in the control file , which has been recorded DBWn modified data blocks from the SGA to disk . This is called ” incremental checkpoints .” Use the checkpoint is to identify the online redo log file to start the instance recovery position ( this position is called a “checkpoint position ” ) . If the log switch occurs , the CKPT process also writes the data file header checkpoint information .
Checkpoints exist due to the following reasons:
• Ensure that the memory has been modified data blocks can be written to disk periodically , so that when a system or database failure is not lost data
• reduction ( online only need to deal with on a checkpoint after the redo log file entries , you can recover. ) The time required for instance recovery
• Ensure that all submitted data will be written during the shutdown data file
CKPT checkpoint process writes information includes the location of the checkpoint , the system change number (SCN), the online redo log file to restore the position of the start , about the log information, etc.
Note : CKPT process does not write data blocks