System Monitor Process (SMON) (120)

The system monitor process (SMON) performs recovery, if necessary, at instance
startup. SMON is also responsible for cleaning up temporary segments that are no
longer in use and for coalescing contiguous free extents within dictionary managed
tablespaces. If any terminated transactions were skipped during instance recovery
because of file-read or offline errors, SMON recovers them when the tablespace or file
is brought back online. SMON checks regularly to see whether it is needed. Other
processes can call SMON if they detect a need for it.
With Real Application Clusters, the SMON process of one instance can perform
instance recovery for a failed CPU or instance.

系統監視程式
主要用來
1. 在例項啟動時恢復
2. 整理不再使用的臨時段
3. 合併dmt下的連續的空閒的段
4. 在表空間或者檔案重新聯機的時候 , 恢復因為檔案錯誤或者離線的終止事務
5. 在檢測到需要使用SMON時 , 其他程式可呼叫SMON

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