触发DBWn写的条件-from 9i sg

最新推荐文章于 2017-12-01 14:23:00 发布

最新推荐文章于 2017-12-01 14:23:00 发布 · 153 阅读

本文详细介绍了DBWn后台进程的各种触发条件，包括增量或正常检查点、脏缓冲区数量达到阈值、扫描过程中找不到空闲缓冲区、超时、RAC环境中的ping请求、表空间离线操作、表空间读取只读模式、删除或截断表等场景。此外还提及了对SYSTEM表空间数据文件的写入情况。

DBWn defers writing to the data files until one of the following events occurs:
? Incremental or normal checkpoint
? The number of dirty buffers reaches a threshold value
? A process scans a specified number of blocks when scanning for free buffers and
cannot find any
? Timeout occurs
? A ping request in Real Application Clusters (RAC) environment
? Placing a normal or temporary tablespace offline
? Placing a tablespace in read-only mode
? Dropping or truncating a table

---- 会写system 表空间的数据文件 ? ALTER TABLESPACE tablespace name BEGIN BACKUP