SMON程式詳解

The system monitor process (SMON) is in charge of a variety of system-level cleanup duties. The duties assigned to SMON include:
smon負責各種各樣系統級別的清理工作。分配給smon的工作包括：


■ Performing instance recovery, if necessary, at instance startup. In an Oracle RAC 
   database, the SMON process of one database instance can perform instance 
   recovery for a failed instance.

如果必要，在例項啟動時，執行例項恢復。在Oracle RAC中，一個資料庫例項的smon程式能夠對一個失敗的例項執行例項恢復。

Recovering terminated transactions that were skipped during instance recovery 
because of file-read or tablespace offline errors. SMON recovers the transactions 
when the tablespace or file is brought back online.

恢復在例項恢復中被跳過的由於讀檔案或表空間離線錯誤而被中斷的會話。當表空間或檔案重新回到online狀態，smon恢復這些中斷的會話。

■ Cleaning up unused temporary segments. For example, Oracle Database allocates 
   extents when creating an index. If the operation fails, then SMON cleans up the 
   temporary space.

清楚不用的臨時段。例如，當建立index時，資料庫分配一些區。如果操作失敗，smon會清除臨時空間。

■ Coalescing contiguous free extents within dictionary-managed tablespaces.

合併連續的基於資料字典管理的表空間的空閒區

SMON checks regularly to see whether it is needed. Other processes can call SMON if they detect a need for it.

smon會根據規則檢查是否被需要，如果其他程式檢測到需要，則就會呼叫SMON程式。