触发DBWn写的条件-from 9i sg

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

<wbr>---- 会写system 表空间的数据文件<br> ? ALTER TABLESPACE tablespace name<wbr> BEGIN BACKUP</wbr></wbr>