DBWn写规则

yaari

DBWn写规则

作为oracle数据文件写入进程，DBWn写规则在百度上有多种版本，其实翻看oracle官方文档。只有2种情况DBWn进程才会写：database buffer cache空间不足和instance 恢复。

The DBWn process writes dirty buffers to diskunder the following conditions:

·      When aserver process cannot find a clean reusable buffer after scanning a thresholdnumber of buffers, it signals DBWn to write. DBWn writes dirty buffers to diskasynchronously if possible while performing other processing.

·      DBWn periodicallywrites buffers to advance the [url=]checkpoint[/url],which is the position in the [url=]redo thread[/url] from which instance recovery begins (see [url=]"Overview of Checkpoints"[/url]). The log position of the checkpoint is determined by theoldest dirty buffer in the buffercache.

f1662

Rockyw

感谢楼主分享！

xianyu166

还有check point的时候