一 不完全恢復講解
在上一篇文章（RMAN備份與恢復之UNDO表空間丟失）中，我們講到UNDO表空間丟失怎麼處理。UNDO表空間是不可脫機的，同樣，SYSTEM表空間也是不可脫機的，所以SYSTEM表空間丟失的處理辦法和UNDO表空間丟失的處理辦法類似，在此不贅述。
RMAN恢復分爲完全恢復和不完全恢復。完全恢復，顧名思義，就是基於全備的基礎上對數據進行恢復。但是真實環境中這樣的恢復用得很少。相反，不完全恢復使用較多。不完全恢復，也就是通過備份文件，恢復某一個誤操作或者是某一段時間丟失的數據。不完全恢復可以基於時間，基於SCN，基於日誌序列號、基於備份控制文件。本文講解基於時間點的不完全恢復。
二 基於時間點的不完全恢復講解
與前面的文章一樣，既然要做恢復，我們首先要有備份文件，我們使用RMAN工具對數據庫進行備份。備份完全後，我們切換到SQL Plus中，打開顯示完整時間的選項，爲什麼要顯示完整時間呢？因爲基於時間點的恢復需要一個時間點，打開這個選項後，一是可以使我們更方便的查看到操作過程中經歷的時間，二是保證時間點選取的精確性。然後我們登錄到SCOTT用戶，創建一張測試表，插入數據，手動提交。注意，我們爲了保證數據的一致性，最好切換到SYS用戶下手動切換日誌（ALTER SYSTEM SWITCH LOGFILE）和手動觸發CKPT（ALTERSYSTEM CHECKPOINT）。好了，數據準備完成，我們此時刪除表，並同時清空回收站，記下刪除表之前的時間點，後面恢復操作要使用到。現在我們強制關閉數據庫，登錄到RMAN中，啓動數據庫到MOUNT狀態，然後查看當前的INCARNATION號，至於INCARNATION號是什麼東西。我們可以這樣理解，每一次RESETLOGS就會使INCARNATION+1，如果想要恢復到之前INCARNATION的scn（或者時間點），就需要先跳轉到之前的INCARNATION。跳轉到之前的INCARNATION，我們可以使用如下命令：RESET DATABASE TO INCARNATION <INCARNATION號>。舉一個不太恰當的比喻，這個INCARNATION就像我們在十字路口，此時我們不知道應該往哪個方向走，如果你一旦走錯，還得回到這個十字路口選取下一條路。此時我們需要編輯恢復腳本，內容就是告訴ORACLE恢復到哪個時間點，並且還原和恢復數據庫。恢復完成後，我們需要使用RESETLOGS方式打開數據庫，此時我們登錄到SQL Plus中，查看錶只中的數據，如果能夠成功查詢到，證明恢復成功。如果不能查詢到，第一考慮時間點是否選擇正確，第二確認INCARNATION號是否正確，第三數據是否保持了一致性。因爲我們重置了日誌，所以需要重新備份數據庫。至此，完整的恢復操作完成。
三 基於時間點的恢復模擬
Step 1，SQL Plus中確保數據庫在歸檔模式，RMAN中備份數據庫
SQL> ARCHIVE LOG LIST; Database log mode Archive Mode Automatic archival Enabled Archive destination USE_DB_RECOVERY_FILE_DEST Oldest online log sequence 68 Next log sequence to archive 70 Current log sequence 70 [oracle@orcl ~]$ uniread rman target / [uniread] Loaded history (2 lines) Recovery Manager: Release 11.2.0.3.0 - Production on Fri Jan 17 09:44:40 2014 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved. connected to target database: LARRRDB (DBID=3428598070) RMAN> BACKUP DATABASE; Starting backup at 17-JAN-14 using target database control file instead of recovery catalog allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=36 device type=DISK channel ORA_DISK_1: starting full datafile backup set channel ORA_DISK_1: specifying datafile(s) in backup set input datafile file number=00001 name=/u01/oracle/oradata/larrrdb/system01.dbf input datafile file number=00003 name=/u01/oracle/oradata/larrrdb/undotbs01.dbf input datafile file number=00002 name=/u01/oracle/oradata/larrrdb/sysaux01.dbf input datafile file number=00004 name=/u01/oracle/oradata/larrrdb/users01.dbf channel ORA_DISK_1: starting piece 1 at 17-JAN-14 channel ORA_DISK_1: finished piece 1 at 17-JAN-14 piece handle=/u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_nnndf_TAG20140117T094447_9fk2rhv7_.bkp tag=TAG20140117T094447 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:04:07 channel ORA_DISK_1: starting full datafile backup set channel ORA_DISK_1: specifying datafile(s) in backup set including current control file in backup set including current SPFILE in backup set channel ORA_DISK_1: starting piece 1 at 17-JAN-14 channel ORA_DISK_1: finished piece 1 at 17-JAN-14 piece handle=/u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_ncsnf_TAG20140117T094447_9fk309p8_.bkp tag=TAG20140117T094447 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03 Finished backup at 17-JAN-14
Step 2，SQL Plus中打開顯示完整時間
SQL> CONN SCOTT/tiger; Connected. SQL> SET TIME ON; 09:53:34 SQL>
Step 3，SQL Plus創建測試表
09:53:34 SQL> CREATE TABLE test(id NUMBER(2),name VARCHAR(20)); Table created. 09:53:59 SQL>
Step 4，SQL Plus插入數據，並提交，爲了保持數據一致性，最好使用sys用戶手動切換日誌（ALTER SYSTEM SWITCHLOGFILE）和觸發CKPT（ALTERSYSTEM CHECKPOINT）
09:53:59 SQL> INSERT INTO test VALUES(1,'justdb'); 1 row created. 09:54:16 SQL> COMMIT; Commit complete. 09:54:25 SQL> SELECT * FROM test; ID NAME ---------- -------------------- 1 justdb 09:54:33 SQL>
Step 5，SQL Plus中刪除測試表
09:54:33 SQL> DROP TABLE test PURGE; Table dropped.
Step 6，SQL Plus中一致性關閉數據庫
10:00:09 SQL> SHUTDOWN IMMEDIATE; Database closed. Database dismounted. ORACLE instance shut down. 10:01:57 SQL>
Step 7，編輯基於時間點恢復的腳本，注意時間點的選取，此處選取爲刪除表的時間點（09:54:33），注意時間點尤其重要
[oracle@orcl ~]$ vim /home/oracle/recover_data_by_time.sql [oracle@orcl ~]$ cat !$ cat /home/oracle/recover_data_by_time.sql RUN { SET UNTIL TIME "to_date('2014-01-17 09:54:33','yyyy-mm-dd hh24:mi:ss')"; RESTORE DATABASE; RECOVER DATABASE; }
Step 8，登錄到RMAN，啓動數據庫到MOUNT狀態
[oracle@orcl ~]$ uniread rman target / [uniread] Loaded history (6 lines) Recovery Manager: Release 11.2.0.3.0 - Production on Fri Jan 17 10:02:22 2014 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved. connected to target database (not started) RMAN> STARTUP MOUNT; Oracle instance started database mounted Total System Global Area 839282688 bytes Fixed Size 2233000 bytes Variable Size 494931288 bytes Database Buffers 339738624 bytes Redo Buffers 2379776 bytes
Step 9，RMAN中查看當前INCARNATION號，注意：如果有其他的操作，以後恢復時應該選取當前查看到的INCARNATION號，使用RESET DATABASE TO INCARNATION <INCARNATION號>命令
RMAN> LIST INCARNATION; using target database control file instead of recovery catalog List of Database Incarnations DB Key Inc Key DB Name DB ID STATUS Reset SCN Reset Time ------- ------- -------- ---------------- --- ---------- ---------- 1 1 LARRRDB 3428598070 CURRENT 1 23-NOV-13
Step 10，RMAN中執行基於時間點的恢復腳本
RMAN> @ /home/oracle/recover_data_by_time.sql @ /home/oracle/recover_data_by_time.sql RMAN> RUN { 2> SET UNTIL TIME "to_date('2014-01-17 09:54:33','yyyy-mm-dd hh24:mi:ss')"; 3> RESTORE DATABASE; 4> RECOVER DATABASE; 5> } executing command: SET until clause Starting restore at 17-JAN-14 allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=21 device type=DISK channel ORA_DISK_1: starting datafile backup set restore channel ORA_DISK_1: specifying datafile(s) to restore from backup set channel ORA_DISK_1: restoring datafile 00001 to /u01/oracle/oradata/larrrdb/system01.dbf channel ORA_DISK_1: restoring datafile 00002 to /u01/oracle/oradata/larrrdb/sysaux01.dbf channel ORA_DISK_1: restoring datafile 00003 to /u01/oracle/oradata/larrrdb/undotbs01.dbf channel ORA_DISK_1: restoring datafile 00004 to /u01/oracle/oradata/larrrdb/users01.dbf channel ORA_DISK_1: reading from backup piece /u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_nnndf_TAG20140117T094447_9fk2rhv7_.bkp channel ORA_DISK_1: piece handle=/u01/oracle/fast_recovery_area/LARRRDB/backupset/2014_01_17/o1_mf_nnndf_TAG20140117T094447_9fk2rhv7_.bkp tag=TAG20140117T094447 channel ORA_DISK_1: restored backup piece 1 channel ORA_DISK_1: restore complete, elapsed time: 00:04:16 Finished restore at 17-JAN-14 Starting recover at 17-JAN-14 using channel ORA_DISK_1 starting media recovery media recovery complete, elapsed time: 00:00:01 Finished recover at 17-JAN-14 RMAN> **end-of-file**
Step 11，RMAN中使用RESETLOGS打開數據庫
RMAN> ALTER DATABASE OPEN RESETLOGS; database opened
Step 12，SQL Plus中查看數據，如果能夠正確地查看到，證明恢復成功
[oracle@orcl ~]$ sqlplus [uniread] Loaded history (66 lines) SQL*Plus: Release 11.2.0.3.0 Production on Fri Jan 17 10:10:53 2014 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, Oracle Label Security, OLAP, Data Mining, Oracle Database Vault and Real Application Testing options SQL> SELECT open_mode FROM v$database; OPEN_MODE -------------------- READ WRITE #這正是被刪除掉的表中的數據 SQL> SELECT * FROM scott.test; ID NAME ---------- -------------------- 1 justdb
Step 13，因爲重置了日誌，我們需要重新在RMAN中備份
[oracle@orcl ~]$ uniread rman target / [uniread] Loaded history (2 lines) Recovery Manager: Release 11.2.0.3.0 - Production on Fri Jan 17 09:44:40 2014 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved. connected to target database: LARRRDB (DBID=3428598070) RMAN> BACKUP DATABASE;
四 相關文章
我的郵箱：[email protected] 新浪微博：@jutdb 微信公衆平臺：JustOracle（微信號：justoracle） 數據庫技術交流羣：336882565（加羣時驗證 From CSDN XXX） All is well 2014年1月17日 By Larry Wen
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