Oracle 10g 參數之 CONTROL_FILE_RECORD_KEEP_TIME

這個參數是控制文件可重用部份的保留策略參數

當一個新的記錄插入可重用部份,但是其中原有的記錄沒有超過此參數的時間,那麼控制文件就會擴展,以容納新的記錄。相反如果超過此參數的時間,就會覆蓋老化的記錄,控制文件不會擴展。
如果設置為0,那麼,控制文件不會擴展,而總是覆蓋,不推薦這樣做。
建議,此參數至少應該大於RMAN恢復窗口的時間設置,或者一次全備的時間,當然,採用catalog的數據庫,受此參數帶來的影響較小,因為即便控制文件丟失,通過catalog也可以恢復數據庫。
默認值 為 7
可以設置的範圍 是 0-365
其中可重用部份記錄的類別有:
  ARCHIVED LOG                       BACKUP CORRUPTION
  BACKUP DATAFILE                    BACKUP PIECE
  BACKUP REDO LOG                    BACKUP SET
  COPY CORRUPTION                    DATAFILE COPY
  DELETED OBJECT                     LOGHISTORY
  OFFLINE RANGE          

CONTROL_FILE_RECORD_KEEP_TIME specifies the minimum number of days before a reusable record in the control file can be reused. In the event a new record needs to be added to a reusable section and the oldest record has not aged enough, the record section expands. If this parameter is set to 0, then reusable sections never expand, and records are reused as needed.
Note:
This parameter applies only to records in the control file that are circularly reusable (such as archive log records and various backup records). It does not apply to records such as datafile, tablespace, and redo thread records, which are never reused unless the corresponding object is dropped from the tablespace.

重新同步catalog與此參數的關係:
此參數的值應該大於重新同步catalog的間隔,否則,會有一些備份信息因覆蓋而丟失
閃回恢復區與此參數的關係:
當一個紀錄超過此參數的設置,就會被刪除,如果沒有超過,閃回恢復區會視圖擴展控制文件,日誌如下:
kccwnc: trying to expand control file section nnnn for Oracle Managed Files
nnnn為控制文件記錄類型的編號
如果控制文件達到最大大小,不可以在擴展大小,則出現警告:
WARNING: Oracle Managed File filename is unknown to control file. This is the result of limitation in control file size that could not keep all recovery area files.
通過改變控制文件block大小和閃回恢復區冗餘策略來避免這個問題。

 

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