Oracle数据恢复顾问（DRA）使用测试
曾经处理过硬盘上数据损坏或者数据丢失的问题么？结果，尽管你还处在诊断和分析问题发生的阶段，最终用户和经理已经联系你，并且希望知道解决问题的大概时间（ETA）了。你是否希望拥有一个简单，并且更为重要的是，快速的方法来诊断和修复这种类型的故障呢？
继续阅读，来了解Oracle数据恢复顾问（DRA）在这种情况下是如何帮助我们的吧！
数据恢复顾问（Data Recovery Advisor）是一款Oracle数据库工具。该工具会自动诊断数据故障，确定并提出相应修复方案，并执行客户要求的修复。以上修复是基于数据故障是一个硬盘上持久性数据的损坏或者丢失。
数据恢复顾问会在遇到问题时，自动采集数据故障信息，并且，协助执行对于故障的修复。你可以手动修复一个数据故障，或者要求数据恢复顾问来为你执行修复动作。
DRA可以通过企业管理器（EM）Grid Control和/或者恢复管理器（RMAN）来访问。本文将概述在RMAN中使用的命令。
在RMAN中，有四种DRA的命令：
•List Failure - 列出先前执行过的故障评估结果。可能的话，重新验证现有故障并关闭它们。
•Advise Failure - 提出手动和自动修复方案。
•Repair Failure - 通过运行由ADVISE FAILURE建议的最佳修复方案来自动修复故障。完成之后会重新验证现有故障。
•Change Failure - 使你可以改变故障的状态。
例如：下面的步骤有关于一次事故，当一个数据文件已经从操作系统上删除，数据库报告错误。
一个select语句执行失败，并报出如下错误：
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’提供了此次问题的详细信息：
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
做为DRA的下一步操作，使用命令'advise failure'，获得修复该问题的建议方案：
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信息中描述了，2个数据文件的缺失，并且建议还原和恢复。
如前所述，DRA可以修复故障。执行修复脚本之前，可以预览所建议的命令：
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';
现在，你可以决定是否手动运行上面的脚本或让DRA来执行修复：
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
一旦成功完成修复脚本，这个问题应该得到解决，并且select语句返回预期的结果：
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