MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
檢視alert日誌,有MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set這樣的提示
配置快取記憶體恢復的持續時間:FAST_START_MTTR_TARGET
快速啟動故障恢復的基礎是快速啟動檢查點的架構。而不是傳統的事件驅動(也就是日誌切換)檢查點,這的確批次寫入,快速啟動檢查點逐漸發生。每個DBWn程式定期寫入緩衝區寫入磁碟,推進檢查點位置。最古老的修改過的塊被寫入首先要保證每一個寫使檢查點前進。快速啟動檢查點消除了與傳統檢查點發生大量寫入和由此產生的I / O峰值。
隨著快速啟動故障恢復功能,FAST_START_MTTR_TARGET初始化引數,簡化了恢復時間的配置從例項或系統故障。FAST_START_MTTR_TARGET指定預期的平均恢復時間(MTTR)的目標,也就是說,時間(以秒為單位)它應該啟動例項並進行快取記憶體恢復。一旦FAST_START_MTTR_TARGET被設定,資料庫管理增量檢查點寫在試圖滿足該目標。如果你選擇了一個有實用價值的FAST_START_MTTR_TARGET,你可以期望你的資料庫恢復,平均而言,在幾秒鐘之約你所選擇的號碼。
注意:
如果使用時初始化引數FAST_START_MTTR_TARGET,必須禁用或刪除FAST_START_IO_TARGET,LOG_CHECKPOINT_INTERVAL和LOG_CHECKPOINT_TIMEOUT
FAST_START_MTTR_TARGET最大值是3600秒(1小時)。如果設定的值超過3600,則Oracle四捨五入到3600秒。
我們可以使用下面方式設定FAST_START_MTTR_TARGET的值:
SQL>ALTER SYSTEM SET FAST_START_MTTR_TARGET=30;
當FAST_START_MTTR_TARGET引數未設定時,自動檢查點調整生效。
通常,如果我們必須嚴格控制例項或節點恢復時間,那麼我們可以設定FAST_START_MTTR_TARGET為期望時間值;如果恢復時間不需要嚴格控制,那麼我們可以不設定FAST_START_MTTR_TARGET引數,從而啟用Oracle10g的自動檢查點調整特性。
SQL> show parameter fast_start_mttr
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
fast_start_mttr_target integer 0
FAST_START_MTTR_TARGET的值為0,即設定為自動檢測點調整
從v$instance_recovery檢視,檢視FAST_START_MTTR_TARGET
SQL> select RECOVERY_ESTIMATED_IOS REIOS,TARGET_MTTR TMTTR,
2 ESTIMATED_MTTR EMTTR,WRITES_MTTR WMTTR,WRITES_OTHER_SETTINGS WOSET,
3 CKPT_BLOCK_WRITES CKPTBW,WRITES_AUTOTUNE WAUTO,WRITES_FULL_THREAD_CKPT WFTCKPT
4 from v$instance_recovery;
REIOS TMTTR EMTTR WMTTR WOSET CKPTBW WAUTO WFTCKPT
---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------
49407 0 68 0 0 3649819 3506125 3130700
在以上檢視中,WRITES_AUTOTUNE欄位值就是指由於自動調整檢查點執行的寫出次數,
而CKPT_BLOCK_WRITES指的則是由於檢查點寫出的Block的數量。
具體資訊,可以參考官方文件
來自 “ ITPUB部落格 ” ,連結:http://blog.itpub.net/29096438/viewspace-1742929/,如需轉載,請註明出處,否則將追究法律責任。
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