Redo file corruption repair

1 inactive The log group is damaged

Suppose the log group 4 damage , state inactive. The solution is simple , Just rebuild the log group
clear It means rebuilding group4 The file of

alter database clear logfile group 4;

2 current The log group is missing

This example log group 1 Status is CURRENT State of , Now simulate the current log group corruption

SQL> select group#,member from v$logfile;
[oracle@bpxtest]$ rm / route /redo01.log
SQL> alter system switch logfile;    Switch several times , Touch it .

The alarm log will record relevant information
There seems to be no problem for the time being , Keep switching , When current Transfer to group1 when ,session die ！
Currently, the problem of log corruption is complex , As shown in the figure above, it can be discussed in the following situations

1） The database did not crash

First step , You can make a complete checkpoint , take db buffer All in dirty buffer Refresh all to disk .

SQL> alter system checkpoint;

The second step , Try to forcibly clear the database without archiving when it is open .

SQL> alter database clear unarchived logfile group n;

The database is now open , If this step succeeds , We must build a new database , Because the current log cannot be archived , Archive log sequence Continuity cannot be maintained . The purpose of full preparation is to get rid of the previous archived logs .

2） The database has crashed , You can only do traditional incomplete log based recovery or use flashback databases .

SQL> recover database until cancel;
SQL> alter database open resetlogs;

3） If there is no backup available before , Or the problem is so serious that no method can resetlogs Open database , To save the data , Consider the last move Oracle Implicit parameters of ：_allow_resetlogs_corruption=TRUE

Oracle This implicit parameter is not recommended
The meaning of this parameter is ： Allow the database to force open the database without sex .
After forcibly opening the database in an inconsistent state , It is suggested to make a logic complete .

3 active The log group is damaged

Do checkpoint switching , If successful , according to inactive Damage handling . otherwise , Press current Damage handling .

Backup recovery Lesson 12. Performing Recovery II