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This article will explain in detail what is the use of dbwr, lgwr and ckpt in the database. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Dbwr:

1. When dirty list reaches a certain amount (threshold 25%), it causes Server Proceess to notify DBWn to write stolen data.

2. When the scan LRU list reaches a certain number and the free buffer is not found, stop searching for free buffer and directly inform DBWn to write dirty data

3. Checkpoint writes data

Lgwr

First, the foreground process triggers

1. The user issues a commit,rollback statement.

two。 The log buffer could not find enough memory to hold the log information.

Two, every 3 seconds

Third, the amount of log information reaches 1 of the log buffer.

Fourth, the amount of log information reaches 1MB.

Fifth, when DBWn starts, if it is found that the redo entries corresponding to dirty data blocks have not been written to the online log file, trigger LGWR, and wait for LGWR to finish writing before DBWn continues.

Ckpt

1. When a log group switch occurs

two。 When the LOG_CHECKPOINT_TIMEOUT,LOG_CHECKPOINT_INTERVAL,fast_start_io_target,fast_start_mttr_target parameter setting is met

3. When running ALTER SYSTEM SWITCH LOGFILE

4. When running ALTER SYSTEM CHECKPOINT

5. When running alter tablespace XXX begin backup,end backup

6. When running alter tablespace, datafile offline

This is the end of the article on "what is the use of dbwr, lgwr and ckpt in the database". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it out for more people to see.

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