Explanation/reference:
Checkpoint process: The checkpoint process (CKPT) updates the control file and data file headers with checkpoint information and Signals DBWN To write blocks to disk. Checkpoint information includes the Checkpoint position, SCN, location in online redo log to begin recovery, and so on. CKPT does not write data blocks to data files or redo blocks to online redo log files.
Check Point function: (1) Regular promotion of the DBWN Process writes the dirty block of memory back to the data file and does not lose data when the database fails (2) Reduce the time of instance recovery (3) Ensure that all submitted data is written to the data file during a consistent shutdown
Instance recovery time: Refers to the time required to push the last checkpoint (checkpoint location) of the data file to the latest SCN recorded in the control file. Administrators can control the time by setting the mttr target and resizing the redo log group.
MTTR: Mean time to Repair, that is, the mean duration of repair. Refers to the average repair time for repairable products, which is the time between failure and repair. The shorter the MTTR, the better the recoverability. In the database, you can control the time it takes for a database to perform a crash recovery on a single instance by setting the parameter Fast_start_mttr_target (in seconds).
Fast_start_mttr_targe= non-0 value, enable the Quick Start Checkpoint feature, automatically control the speed of the check point. Fast_start_mttr_targe=0, disable the Quick Start checkpoint feature.
If the redo log file size is too small to switch logs frequently, checkpoints frequently occur, so you can increase the size of the redo log file to reduce the frequency at which checkpoints occur.
Fast_start_mttr_target if the setting is too small, in order to control the instance recovery time of a database singleton, checkpoints must occur frequently to ensure that the modified chunks of memory are regularly written to disk, so you can use the MTTR advisor to set the recommended values. |