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current online redo logfile 丢失的处理方法
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昨天做了rm -rf操作后的恢复演练，并且是在没有不论什么备份的情况下。今天在做破坏性操作前，做了个rman全备，然后在线删除所有数据库文件，包含控制文件，数据文件，在线日志文件，归档文件等。来看看有什么方法能够让数据库恢复执行，因为是current redo logfile丢失，那么本次測试是会丢失数据的，所以能够作为不全然恢复的一个案例。
--登入数据库进行dml操作
[oracle@ora10g ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Aug 26 13:40:37 2014
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> select * from aaron8219.test1;
INT
----------
1
2
SQL> insert into aaron8219.test1 values(3);
1 row created.
SQL> select group#,status,sequence# from v$log;
GROUP# STATUS SEQUENCE#
---------- ---------------- ----------
1 INACTIVE 1
2 CURRENT 2
3 INACTIVE 0
--不提交，另开一个session进行rm -rf操作
[root@ora10g ~]# cd /u01/app/oracle/oradata
[root@ora10g oradata]# ll
total 4
drwxr-x--- 2 oracle oinstall 4096 Aug 25 16:09 ora10g
[root@ora10g oradata]# rm -rf ora10g/
[root@ora10g oradata]# ll
total 0
--原session直接abort关闭，模拟current online redo logfile丢失
SQL> shutdown abort
--用之前刚生成的rman全备来还原数据库各类文件
[oracle@ora10g ~]$ rman target /
Recovery Manager: Release 10.2.0.1.0 - Production on Tue Aug 26 13:44:58 2014
Copyright (c) 1982, 2005, Oracle. All rights reserved.
connected to target database: ora10g (not mounted)
RMAN> restore controlfile from '/rmanbak/full_ORA10G_4175411955_20140826_02pgtq5h_1_1.bak';
Starting restore at 26-AUG-14
using channel ORA_DISK_1
channel ORA_DISK_1: restoring control file
channel ORA_DISK_1: restore complete, elapsed time: 00:00:04
output filename=/u01/app/oracle/oradata/ora10g/control01.ctl
output filename=/u01/app/oracle/oradata/ora10g/control02.ctl
output filename=/u01/app/oracle/oradata/ora10g/control03.ctl
Finished restore at 26-AUG-14
RMAN> alter database mount;
database mounted
released channel: ORA_DISK_1
RMAN> restore database;
Starting restore at 26-AUG-14
Starting implicit crosscheck backup at 26-AUG-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=156 devtype=DISK
Crosschecked 1 objects
Finished implicit crosscheck backup at 26-AUG-14
Starting implicit crosscheck copy at 26-AUG-14
using channel ORA_DISK_1
Finished implicit crosscheck copy at 26-AUG-14
searching for all files in the recovery area
cataloging files...
cataloging done
List of Cataloged Files
=======================
File Name: /u01/app/oracle/flash_recovery_area/ORA10G/autobackup/2014_08_26/o1_mf_s_856615092_9zr3snsq_.bkp
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile backupset restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
restoring datafile 00001 to /u01/app/oracle/oradata/ora10g/system01.dbf
restoring datafile 00002 to /u01/app/oracle/oradata/ora10g/undotbs01.dbf
restoring datafile 00003 to /u01/app/oracle/oradata/ora10g/sysaux01.dbf
restoring datafile 00004 to /u01/app/oracle/oradata/ora10g/users01.dbf
restoring datafile 00005 to /u01/app/oracle/oradata/ora10g/example01.dbf
channel ORA_DISK_1: reading from backup piece /rmanbak/full_ORA10G_4175411955_20140826_01pgtq36_1_1.bak
channel ORA_DISK_1: restored backup piece 1
piece handle=/rmanbak/full_ORA10G_4175411955_20140826_01pgtq36_1_1.bak tag=TAG20140826T123653
channel ORA_DISK_1: restore complete, elapsed time: 00:01:46
Finished restore at 26-AUG-14
RMAN> exit
Recovery Manager complete.
因为rman并不备份在线日志文件，刚才的rman仅仅是做了个全库备份和控制文件的备份，能够看到redo01.log，redo02.log，redo03.log这3个文件并不存在
[oracle@ora10g ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Aug 26 14:52:35 2014
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> select open_mode from v$database;
OPEN_MODE
----------
MOUNTED
SQL> col member for a60
SQL> select group#,member from v$logfile;
GROUP# MEMBER
---------- ------------------------------------------------------------
3 /u01/app/oracle/oradata/ora10g/redo03.log
2 /u01/app/oracle/oradata/ora10g/redo02.log
1 /u01/app/oracle/oradata/ora10g/redo01.log
SQL> alter database open resetlogs;
alter database open resetlogs
*
ERROR at line 1:
ORA-01152: file 1 was not restored from a sufficiently old backup
ORA-01110: data file 1: '/u01/app/oracle/oradata/ora10g/system01.dbf'
因为仅仅是restore了数据库，还未recover，数据库是无法打开的
SQL> recover database
ORA-00283: recovery session canceled due to errors
ORA-01610: recovery using the BACKUP CONTROLFILE option must be done
SQL> recover database until cancel;
ORA-00283: recovery session canceled due to errors
ORA-01610: recovery using the BACKUP CONTROLFILE option must be done
SQL> recover database using backup controlfile;
ORA-00279: change 502729 generated at 08/26/2014 15:36:54 needed for thread 1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/ORA10G/archivelog/2014_08_26/o1_mf_1_3_%u_.arc
ORA-00280: change 502729 for thread 1 is in sequence #3
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00308: cannot open archived log
'/u01/app/oracle/flash_recovery_area/ORA10G/archivelog/2014_08_26/o1_mf_1_3_%u_.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
ORA-00308: cannot open archived log
'/u01/app/oracle/flash_recovery_area/ORA10G/archivelog/2014_08_26/o1_mf_1_3_%u_.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
SQL> recover database using backup controlfile until cancel;
ORA-00279: change 502729 generated at 08/26/2014 15:36:54 needed for thread 1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/ORA10G/archivelog/2014_08_26/o1_mf_1_3_%u_.arc
ORA-00280: change 502729 for thread 1 is in sequence #3
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
cancel
Media recovery cancelled.
SQL>
因为之前的归档没实用rman备份，而如今也不存在了，无法recover数据库，就算用resetlogs也无法open数据库。此时，仅仅有通过隐含參数_allow_resetlogs_corruption来open数据库了
SQL> show parameter spfile
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string /u01/app/oracle/product/10.2.0
/db_1/dbs/spfileora10g.ora
--创建pfile
SQL> create pfile from spfile;
File created.
--编辑$ORACLE_HOME/dbs/initora10g.ora初始化參数文件，在文件末尾加入*._allow_resetlogs_corruption = true
[oracle@ora10g ora10g]$ vi $ORACLE_HOME/dbs/initora10g.ora
ora10g.__db_cache_size=180355072
ora10g.__java_pool_size=4194304
ora10g.__large_pool_size=4194304
ora10g.__shared_pool_size=92274688
ora10g.__streams_pool_size=0
*.audit_file_dest='/u01/app/oracle/admin/ora10g/adump'
*.background_dump_dest='/u01/app/oracle/admin/ora10g/bdump'
*.compatible='10.2.0.1.0'
*.control_files='/u01/app/oracle/oradata/ora10g/control01.ctl','/u01/app/oracle/oradata/ora10g/control02.ctl','/u01/app/oracle/oradata/ora10g/control03.ctl'#Restore Controlfile
*.core_dump_dest='/u01/app/oracle/admin/ora10g/cdump'
*.db_block_size=8192
*.db_domain=''
*.db_file_multiblock_read_count=16
*.db_name='ora10g'
*.db_recovery_file_dest='/u01/app/oracle/flash_recovery_area'
*.db_recovery_file_dest_size=2147483648
*.dispatchers='(PROTOCOL=TCP) (SERVICE=ora10gXDB)'
*.job_queue_processes=10
*.log_archive_format='%t_%s_%r.dbf'
*.nls_language='SIMPLIFIED CHINESE'
*.nls_territory='CHINA'
*.open_cursors=300
*.pga_aggregate_target=94371840
*.processes=150
*.remote_login_passwordfile='EXCLUSIVE'
*.sga_target=285212672
*.undo_management='AUTO'
*.undo_tablespace='UNDOTBS1'
*.user_dump_dest='/u01/app/oracle/admin/ora10g/udump'
*._allow_resetlogs_corruption=TRUE
--关闭数据库实例，用pfile启动
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup pfile=$ORACLE_HOME/dbs/initora10g.ora
ORACLE instance started.
Total System Global Area 285212672 bytes
Fixed Size 1218992 bytes
Variable Size 100664912 bytes
Database Buffers 180355072 bytes
Redo Buffers 2973696 bytes
Database mounted.
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
--最后用resetlogs打开数据库
SQL> alter database open resetlogs;
Database altered.
SQL>
[oracle@ora10g ora10g]$ ll
total 1051020
-rw-r----- 1 oracle oinstall 7061504 Aug 26 16:03 control01.ctl
-rw-r----- 1 oracle oinstall 7061504 Aug 26 16:03 control02.ctl
-rw-r----- 1 oracle oinstall 7061504 Aug 26 16:03 control03.ctl
-rw-r----- 1 oracle oinstall 104865792 Aug 26 16:03 example01.dbf
-rw-r----- 1 oracle oinstall 52429312 Aug 26 16:03 redo01.log
-rw-r----- 1 oracle oinstall 52429312 Aug 26 16:03 redo02.log
-rw-r----- 1 oracle oinstall 52429312 Aug 26 16:03 redo03.log
-rw-r----- 1 oracle oinstall 251666432 Aug 26 16:03 sysaux01.dbf
-rw-r----- 1 oracle oinstall 503324672 Aug 26 16:03 system01.dbf
-rw-r----- 1 oracle oinstall 20979712 Aug 26 16:03 temp01.dbf
-rw-r----- 1 oracle oinstall 31465472 Aug 26 16:03 undotbs01.dbf
-rw-r----- 1 oracle oinstall 5251072 Aug 26 16:03 users01.dbf
[oracle@ora10g ora10g]$
再次查看数据文件，发现又一次生成了3个online redo logfile了
--resetlogs把SEQUENCE#序列号又一次变成1
SQL> select group#,sequence# from v$log;
GROUP# SEQUENCE#
---------- ----------
1 0
2 1
3 0
--測试表仅仅留下了原来的数据库，由于没有commit，新插入的第3条记录丢失，就算commit，也是会丢数据的，由于redo logfile也被删除了
SQL> select * from aaron8219.test1;
INT
----------
1
2
注意，最后要把刚才设置的隐含參数_allow_resetlogs_corruption = true去掉，并又一次创建spfile，否则数据库将来会有引起不一致的风险，设置该隐含參数仅仅是下下策，为了能让数据库open而不得已为之，丢失数据库是肯定的了，由于这是在极端情况下得測试，通常仅仅有在丢失了状态为current的online redo logfile才会丢失数据，假设仅仅是inactive的redo logfile，就算使用alter database
open resetlogs;也不意味着100%丢数据。另外，要注意的是，当使用using backup controlfile关键词时，必需要配合使用open resetlogs来打开数据库。以resetlogs方式open数据库后，必须又一次做一次数据库全备，由于一旦incarnation改变之后，数据库原来的备份集就失效了。
