Oracle資料恢復顧問（DRA）使用測試 (之一)

曾經處理過硬碟上資料損壞或者資料丟失的問題麼？結果，儘管你還處在診斷和分析問題發生的階段，終端使用者和經理已經聯絡你，並且希望知道解決問題的大概時間（ETA）了。你是否希望擁有一個簡單，並且更為重要的是，快速的方法來診斷和修復這種型別的故障呢？
                繼續閱讀，來了解Oracle資料恢復顧問（DRA）在這種情況下是如何幫助我們的吧！

資料恢復顧問（Data Recovery Advisor）是一款Oracle資料庫工具。該工具會自動診斷資料故障，確定並提出相應修復方案，並執行客戶要求的修復。以上修復是基於資料故障是一個硬碟上永續性資料的損壞或者丟失。               

資料恢復顧問會在遇到問題時，自動採集資料故障資訊，並且，協助執行對於故障的修復。你可以手動修復一個資料故障，或者要求資料恢復顧問來為你執行修復動作。              

DRA可以透過企業管理器（EM）Grid Control和/或者恢復管理器（RMAN）來訪問。本文將概述在RMAN中使用的命令。

在RMAN中，有四種DRA的命令：

• List Failure - 列出先前執行過的故障評估結果。可能的話，重新驗證現有故障並關閉它們。
• Advise Failure - 提出手動和自動修復方案。
• Repair Failure - 透過執行由ADVISE FAILURE建議的最佳修復方案來自動修復故障。完成之後會重新驗證現有故障。
• Change Failure - 使你可以改變故障的狀態。

例如：下面的步驟有關於一次事故，當一個資料檔案已經從作業系統上刪除，資料庫報告錯誤。

一個select語句執行失敗，並報出如下錯誤：

 SQL> select * from emp;
   select * from emp
   *
   ERROR at line 1:
   ORA-01116: error in opening database file 4
   ORA-01110: data file 4: '/u01/V112_oradata/users01.dbf'
   ORA-27041: unable to open file
   Linux Error: 2: No such file or directory
   Additional information: 3 

  DRA命令‘list failure’提供了此次問題的詳細資訊：

 Recovery Manager: Release 11.2.0.3.0 - Production on Wed Aug 21 10:12:36 2013
   Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

   connected to target database: V112 (DBID=2335388877)

   RMAN> list failure;

   using target database control file instead of recovery catalog
   List of Database Failures
   =========================
   Failure ID Priority Status    Time      Detected Summary
   ---------- -------- --------- --------- --------------------------------------------
   82         HIGH     OPEN      21-AUG-13 One or more non-system datafiles are missing 

做為DRA的下一步操作，使用命令'advise failure'，獲得修復該問題的建議方案：

 RMAN> advise failure;

   List of Database Failures
   =========================

   Failure ID Priority Status    Time Detected Summary
   ---------- -------- --------- ------------- -------
   82         HIGH     OPEN      21-AUG-13     One or more non-system datafiles are missing

   analyzing automatic repair options; this may take some time
   allocated channel: ORA_DISK_1
   channel ORA_DISK_1: SID=28 device type=DISK
   analyzing automatic repair options complete

   Mandatory Manual Actions
   ========================
   no manual actions available

   Optional Manual Actions
   =======================
   1. If file /u01/V112_oradata/users01.dbf was unintentionally renamed or moved, restore it
   2. If file /u01/V112_oradata/test01.dbf was unintentionally renamed or moved, restore it

   Automated Repair Options
   ========================
   Option Repair Description
   ------ ------------------
   1 Restore and recover datafile 4; Restore and recover datafile 5
    Strategy: The repair includes complete media recovery with no data loss
    Repair script: /u02/app/oracle/diag/rdbms/v112/V112/hm/reco_1311249797.hm 

DRA資訊中描述了，2個資料檔案的缺失，並且建議還原和恢復。

如前所述，DRA可以修復故障。執行修復指令碼之前，可以預覽所建議的命令：

 RMAN> repair failure preview;

   Strategy: The repair includes complete media recovery with no data loss
   Repair script: /u02/app/oracle/diag/rdbms/v112/V112/hm/reco_1311249797.hm

   contents of repair script:
    # restore and recover datafile
    sql 'alter database datafile 4, 5 offline';
    restore datafile 4, 5;
    recover datafile 4, 5;
    sql 'alter database datafile 4, 5 online'; 

現在，你可以決定是否手動執行上面的指令碼或讓DRA來執行修復：

 RMAN> repair failure;

   Strategy: The repair includes complete media recovery with no data loss
   Repair script: /u02/app/oracle/diag/rdbms/v112/V112/hm/reco_1311249797.hm

   contents of repair script:
    # restore and recover datafile
    sql 'alter database datafile 4, 5 offline';
    restore datafile 4, 5;
    recover datafile 4, 5;
    sql 'alter database datafile 4, 5 online';

   Do you really want to execute the above repair (enter YES or NO)? yes
   executing repair script

   sql statement: alter database datafile 4, 5 offline

   Starting restore at 21-AUG-13
   using channel ORA_DISK_1

   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 00004 to /u01/V112_oradata/users01.dbf
   channel ORA_DISK_1: restoring datafile 00005 to /u01/V112_oradata/test01.dbf
   channel ORA_DISK_1: reading from backup piece 
   /u01/temp/flash_areas/V112/V112/backupset/2013_08_21/o1_mf_nnndf_TAG20130821T100251_919l4f2p_.bkp
   channel ORA_DISK_1: piece
   handle=/u01/temp/flash_areas/V112/V112/backupset/2013_08_21/o1_mf_nnndf_TAG20130821T100251_919l4f2p_.bkp
   tag=TAG20130821T100251
   channel ORA_DISK_1: restored backup piece 1
   channel ORA_DISK_1: restore  complete, elapsed time: 00:00:35
   Finished restore at 21-AUG-13

   Starting recover at 21-AUG-13
   using channel ORA_DISK_1

   archived log for thread 1 with sequence 79 is already on disk as file 
   /u01/temp/flash_areas/V112/V112/archivelog/2013_08_21/o1_mf_1_79_919lm6y2_.arc
   channel ORA_DISK_1: starting archived log restore to default destination
   channel ORA_DISK_1: restoring archived log
   archived log thread=1 sequence=77
   channel ORA_DISK_1: restoring archived log
   archived log thread=1 sequence=78
   channel ORA_DISK_1: reading from backup piece 
   /u01/temp/flash_areas/V112/V112/backupset/2013_08_21/o1_mf_annnn_TAG20130821T101028_919llo3n_.bkp
   channel ORA_DISK_1: piece 
   handle=/u01/temp/flash_areas/V112/V112/backupset/2013_08_21/o1_mf_annnn_TAG20130821T101028_919llo3n_.bkp
   tag=TAG20130821T101028
   channel ORA_DISK_1: restored backup piece 1
   channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
   archived log file name=/u01/temp/flash_areas/V112/V112/archivelog/2013_08_21/o1_mf_1_77_919ltj5h_.arc
   thread=1 sequence=77
   channel default: deleting archived log(s)
   archived log file name=/u01/temp/flash_areas/V112/V112/archivelog/2013_08_21/o1_mf_1_77_919ltj5h_.arc 
   RECID=50 STAMP=824033680
   archived log file name=/u01/temp/flash_areas/V112/V112/archivelog/2013_08_21/o1_mf_1_78_919ltj7o_.arc 
   thread=1 sequence=78
   channel default: deleting archived log(s)
   archived log file name=/u01/temp/flash_areas/V112/V112/archivelog/2013_08_21/o1_mf_1_78_919ltj7o_.arc 
   RECID=51 STAMP=824033680
   media recovery complete, elapsed  time: 00:00:00
   Finished recover at 21-AUG-13

   sql statement: alter database       datafile 4, 5 online
   repair failure complete 

一旦成功完成修復指令碼，這個問題應該得到解決，並且select語句返回預期的結果：

 SQL> select * from emp;
   EMPNO ENAME    JOB       MGR   HIREDATE  SAL  COMM  DEPTNO
   ----- -------- --------- ----- --------- ---- ----- ------
    7900 JAMES    CLERK     7698  03-DEC-81  950       30
    7902 FORD     ANALYST   7566  03-DEC-81 3000       20
    7934 MILLER   CLERK     7782  23-JAN-82 1300       10