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數(shù)據(jù)庫引航第七課—Oracle數(shù)據(jù)庫對象（二）2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
1重做日志--REDO2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
2REDO2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
3REDO--日志組2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
4REDO和歸檔2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
5REDO的內(nèi)容---改變向量2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
6REDO--undo的redo2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
7UNDO?作用–數(shù)據(jù)的回滾–一致性讀–表的閃回（事務，查詢的閃回....)–失敗會話的恢復2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
8Undo的產(chǎn)生2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
9UndoV.S.RedoUndoRedoRecordofHowtoundoachangeHowtoreproduceachangeUsedforRollback,readconsistency,RollingforwardflashbackdatabasechangesStoredinUndosegmentsRedologfilesProtectsInconsistentreadsinDatalossUndoagainstmultiusersystemssegmentRedologfiles2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
10RedoBufferOperationWhenuserenters…User#1dataundodatafile2file3file4UPDATEemp1234XYZ5ZackSETsal=10WHEREid=1234databasebuffercache1-11Copyright?OracleCorporation,2002.Allrightsreserved.
11RedoBufferOperationWhenuserenters…User#1dataundodatafile2file3file4UPDATEemp1234XYZ5ZackSETsal=10WHEREid=1234Thedatablockisretrievedfromdisktothedatabase1234buffercache(unlessit’s5alreadythere)databasebuffercache1-12Copyright?OracleCorporation,2002.Allrightsreserved.
12RedoBufferOperationWhenuserenters…User#1dataundodatafile2file3file4UPDATEemp1234XYZ5ZackSETsal=10WHEREid=1234Thedatablockisretrievedfromdisktothedatabase1234buffercache(unlessit’s5alreadythere)U1Theundoblockisthenretrievedfromdisktothedatabasebuffercache(unlessit’salreadythere)databasebuffercache1-13Copyright?OracleCorporation,2002.Allrightsreserved.
13RedoBufferOperationWhenuserenters…User#1dataundodatafile2file3file4UPDATEemp1234XYZ5ZackSETsal=10WHEREid=1234Thedatablockisretrievedfromdisktothedatabase1234buffercache(unlessit’s5alreadythere)U1Theundoblockis5thenretrievedfromdisktothedatabasebuffercache(unlessit’salreadythere)Theundodataiscreatedshowingthe‘beforeimage’databasebuffercache1-14Copyright?OracleCorporation,2002.Allrightsreserved.
14RedoBufferOperationWhenuserenters…RedoBufferUser#1dataundodataTranFileBlockRowColumnValuefile2file3file4idUPDATEemp1234XYZ5ZackT1312--5SETsal=10WHEREid=1234Thedatablockisretrievedfromdisktothedatabase1234buffercache(unlessit’s5alreadythere)U1Theudoblockis5thenretrievedfromdisktothedatabasebuffercache(unlessit’salreadythere)Theundodataiscreatedshowingthe‘beforeimage’AndanentryrecordingthischangeismadeindatabasebuffercachetheREDObuffer1-15Copyright?OracleCorporation,2002.Allrightsreserved.
15RedoBufferOperationWhenuserenters…RedoBufferUser#1dataundodataTranFileBlockRowColumnValuefile2file3file4idUPDATEemp1234XYZ5ZackT1312--5SETsal=10WHEREid=12341234Thenthedatablockis5xchanged...10U15databasebuffercache1-16Copyright?OracleCorporation,2002.Allrightsreserved.
16RedoBufferOperationWhenuserenters…RedoBufferUser#1dataundodataTranFileBlockRowColumnValuefile2file3file4idUPDATEemp1234XYZ5ZackT1312--5SETsal=10T1212341610WHEREid=12341234Thenthedatablockis5xchanged...10AndanentryrecordingU15thischangeismadeintheREDObufferdatabasebuffercache1-17Copyright?OracleCorporation,2002.Allrightsreserved.
17Undo表空間?普通的數(shù)據(jù)表空間?機制和數(shù)據(jù)表空間完全一致，只不過用途不同。2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
18自動管理回滾段表空間?動態(tài)改變回滾段的個數(shù)。?自動調(diào)整回滾段的大小2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
19Undo數(shù)據(jù)的保留時間2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
20Undo表空間的損壞?如果有活動的事務，需要恢復Undo表空間，如果沒有備份，將導致數(shù)據(jù)庫損壞。?如果沒有活動事務，可以重建一個undo表空間。2012.10.15DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
21ThanksFAQ時間DATAGURU專業(yè)數(shù)據(jù)分析網(wǎng)站
