active redo.log丢失的一些问题
实验1SQL> select * from v$log;
GROUP# THREAD#SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
1 1 35 52428800 1 YES INACTIVE 872466 03-JUN-12
2 1 37 52428800 1 NOCURRENT 872476 03-JUN-12
3 1 34 52428800 1 YES INACTIVE 872459 03-JUN-12
4 1 36 52428800 1 YES ACTIVE 872472 03-JUN-12
SQL> shutdown abort;
ORACLE instance shut down.
先shutdown abort,再删除redo04.log
SQL> startup
ORACLE instance started.
Total System Global Area285212672 bytes
Fixed Size 1218992 bytes
Variable Size 104859216 bytes
Database Buffers 176160768 bytes
Redo Buffers 2973696 bytes
Database mounted.
ORA-00313: open failed for members of log group 4 of thread 1
ORA-00312: online log 4 thread 1: '/u01/app/oracle/oradata/ora10g/redo04.log'
SQL> select * from v$log;
GROUP# THREAD#SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
1 1 35 52428800 1 YES INACTIVE 872466 03-JUN-12
4 1 36 52428800 1 YES INACTIVE 872472 03-JUN-12
3 1 34 52428800 1 YES INACTIVE 872459 03-JUN-12
2 1 37 52428800 1 NOCURRENT 872476 03-JUN-12
shutdown abort不是一个类似于断电的操作吗，为什么redo04的状态由active变成了inactive了呢?
SQL> alter database clear logfile group 4;
Database altered.
SQL> alter database open;
Database altered.
实验2
SQL> select * from v$log;
GROUP# THREAD#SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
1 1 35 52428800 1 YES INACTIVE 872466 03-JUN-12
2 1 37 52428800 1 YES INACTIVE 872476 03-JUN-12
3 1 39 52428800 1 NOCURRENT 892634 03-JUN-12
4 1 38 52428800 1 YES ACTIVE 892483 03-JUN-12
先删除redo04.log,然后再shutdown abort
SQL> shutdown abort
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area285212672 bytes
Fixed Size 1218992 bytes
Variable Size 104859216 bytes
Database Buffers 176160768 bytes
Redo Buffers 2973696 bytes
Database mounted.
ORA-00313: open failed for members of log group 4 of thread 1
ORA-00312: online log 4 thread 1: '/u01/app/oracle/oradata/ora10g/redo04.log'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
和实验1的错误不同了
SQL> select * from v$log;
GROUP# THREAD#SEQUENCE# BYTES MEMBERS ARC STATUS FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
1 1 35 52428800 1 YES INACTIVE 872466 03-JUN-12
4 1 38 52428800 1 YES ACTIVE 892483 03-JUN-12
3 1 39 52428800 1 NOCURRENT 892634 03-JUN-12
2 1 37 52428800 1 YES INACTIVE 872476 03-JUN-12
SQL> alter database clear logfile group 4;
alter database clear logfile group 4
*
ERROR at line 1:
ORA-01624: log 4 needed for crash recovery of instance ora10g (thread 1)
ORA-00312: online log 4 thread 1: '/u01/app/oracle/oradata/ora10g/redo04.log'
如果真是这个情况，是不是只能做不完全恢复了呢？ 是否是inactive，主要看的是控制文件的ckpt scn是否落在日志文件的first scn和last scn之间，第一个实验应该是redo4对应的脏数据块已经写入到了数据文件中，但是v$log还没有反映出来。
启动以后，这个很容易判断出来，因为你的控制文件没有问题。
第二个实验是一个正常的实验，数据库只能做不完全恢复了。
第一个实验是一个偶然因素，但是你要知道原因。 你主要记住第二个实验就行了，第一个实验没有具体的实战意义。 谢谢老师指点！我已经明白了。
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