Oracle基於Cancel的不完全恢復

oracle

實驗時間：2011-10-14　環境：RED HAT4，Oracle 10.0.20

基於Cancel的不完全恢復適用場景：Recover時，所需的某個歸檔日誌損壞，或主機斷電，current狀態的聯機日誌損壞。

一、環境準備
以SCOTT用戶登錄，新建表EMP1，切換日誌，再新建表EMP2，主機斷電，刪除當前日誌文件，模擬文件損壞。具體命令如下：
SQL> conn scott/oracle
Connected.
SQL> create table emp1 as select * from emp;

Table created.

SQL> conn / as sysdba
Connected.
SQL> alter system switch logfile;

System altered.
SQL> conn scott/oracle
Connected.
SQL> create table emp2 as select * from emp;

Table created.
SQL> conn / as sysdba
Connected.

確認日誌的位置。
SQL> select * from v$log;

    GROUP#    THREAD#  SEQUENCE#      BYTES    MEMBERS ARC STATUS           FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
         1          1          5   52428800          1 NO  CURRENT                 916653 14-OCT-11
         2          1          4   52428800          1 YES ACTIVE                  915569 14-OCT-11
         3          1          3   52428800          1 YES INACTIVE                915566 14-OCT-11

SQL> select * from v$logfile;

    GROUP# STATUS  TYPE    MEMBER                                                       IS_
---------- ------- ------- ------------------------------------------------------------ ---
         3         ONLINE  /home/oracle/oracle/product/oradata/orcl/redo03.log          NO
         2         ONLINE  /home/oracle/oracle/product/oradata/orcl/redo02.log          NO
         1         ONLINE  /home/oracle/oracle/product/oradata/orcl/redo01.log          NO     
        
SQL> shutdown abort
ORACLE instance shut down.
SQL> !rm -f /home/oracle/oracle/product/oradata/orcl/redo02.log

二、恢復步驟
１、嘗試打開數據庫
SQL> startup
ORACLE instance started.

Total System Global Area  130023424 bytes
Fixed Size                  1218100 bytes
Variable Size              67111372 bytes
Database Buffers           58720256 bytes
Redo Buffers                2973696 bytes
Database mounted.
ORA-00313: open failed for members of log group 2 of thread 1
ORA-00312: online log 2 thread 1: '/home/oracle/oracle/product/oradata/orcl/redo02.log'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3

２、嘗試Clear
SQL> alter database clear logfile group 2;
alter database clear logfile group 2
*
ERROR at line 1:
ORA-01624: log 2 needed for crash recovery of instance orcl (thread 1)
ORA-00312: online log 2 thread 1: '/home/oracle/oracle/product/oradata/orcl/redo02.log'
結果提示日誌有用，不能Clear

３、在當前庫做基於Cancel的不完全恢復（這個想法是錯誤的）
SQL> recover database until cancel;
ORA-00279: change 916503 generated at 10/14/2011 23:26:00 needed for thread 1
ORA-00289: suggestion : /home/oracle/oracle/product/archive/1_4_764549776.dbf
ORA-00280: change 916503 for thread 1 is in sequence #4


Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 916653 generated at 10/14/2011 23:26:58 needed for thread 1
ORA-00289: suggestion : /home/oracle/oracle/product/archive/1_5_764549776.dbf
ORA-00280: change 916653 for thread 1 is in sequence #5
ORA-00278: log file '/home/oracle/oracle/product/archive/1_4_764549776.dbf' no longer needed for this recovery


ORA-00308: cannot open archived log '/home/oracle/oracle/product/archive/1_5_764549776.dbf'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3


ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/home/oracle/oracle/product/oradata/orcl/system01.dbf'


SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open


SQL> alter database open resetlogs;
alter database open resetlogs
*
ERROR at line 1:
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/home/oracle/oracle/product/oradata/orcl/system01.dbf'
恢復之後，使用Resetlogs選項，仍無法打開數據庫，提示數據文件不一致，System表空間需要進一步的恢復。
當前日誌損壞時，不能基於當前的數據庫做不完全恢復。只能用以前的備份，做一個基於Cancel的不完全恢復。

４、用以前的備份，做基於Cancel的不完全恢復(其實就是恢復到不能恢復爲止)
SQL> shutdown abort
ORACLE instance shut down.
SQL> !cp /disk2/oracle/coldbak/*.dbf $ORACLE_BASE/oradata/orcl/

SQL> startup mount
ORACLE instance started.

Total System Global Area  130023424 bytes
Fixed Size                  1218100 bytes
Variable Size              67111372 bytes
Database Buffers           58720256 bytes
Redo Buffers                2973696 bytes
Database mounted.
SQL> recover database until cancel;
ORA-00279: change 916502 generated at 10/14/2011 23:13:45 needed for thread 1
ORA-00289: suggestion : /home/oracle/oracle/product/archive/1_4_764549776.dbf
ORA-00280: change 916502 for thread 1 is in sequence #4


Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 916653 generated at 10/14/2011 23:26:58 needed for thread 1
ORA-00289: suggestion : /home/oracle/oracle/product/archive/1_5_764549776.dbf
ORA-00280: change 916653 for thread 1 is in sequence #5
ORA-00278: log file '/home/oracle/oracle/product/archive/1_4_764549776.dbf' no longer needed for this recovery


ORA-00308: cannot open archived log '/home/oracle/oracle/product/archive/1_5_764549776.dbf'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3


SQL> alter database open resetlogs;

Database altered.
可以看到，最後數據可以打開了。

５、檢查數據
SQL> conn scott/oracle
Connected.
SQL> select * from tab;

TNAME                          TABTYPE  CLUSTERID
------------------------------ ------- ----------
DEPT                           TABLE
EMP                            TABLE
BONUS                          TABLE
SALGRADE                       TABLE
RECOVER_TEST                   TABLE
RECOVER_TEST2                  TABLE
EMP_BAK                        TABLE
EMP1                           TABLE

8 rows selected.
可以看到表EMP1存在，表EMP2不存在。因爲EMP2的創建，是保存在當前REDO日誌中的，而當前REDO日誌損壞，所有當前日誌中保存的操作全部丟失了。
歸檔日誌、或者REDO日誌損失，數據庫就只能恢復到丟失的日誌之前了。

數據庫打開的前提之一：數據文件保持一致。當前數據庫不一致無法打開數據庫，只能根據以前一致的備份，恢復到最近的一致的時間點。