We all know that redo log has three kinds of a group like active, inactive, current. They all have different use and as well as different meaning.Let’s simulate a loss of all redo log members of an inactive group.
If you have completely lost one redo log group your database won’t be able to open.
Next thing is to know the STATUS of the lost redo log group (we know it because we are simulating the loss, but…) and, just because this information is on V$LOG view, try to get also the ARCHIVED column.
Now if the redo log group lost was INACTIVE and archived (YES value) we can simply recreate all members with the “alter database clear logfile” command;
if it was INACTIVE and not archived (NO value) we’ll execute the “alter database clear unarchived logfile” command.
Let’s look at the example. Here is my redo log group state
SQL> select member, a.group#, a.status, b.status, a.archived from v$log a, v$logfile b where a.group# = b.group# order by a.group#, member; MEMBER GROUP# STATUS STATUS ARC ------------------------------------------------------------ ---------- ---------------- ------- --- /home/oracle/app/oracle/oradata/orcl/redo01.log 1 INACTIVE YES /home/oracle/app/oracle/oradata/orcl/redo01b.log 1 INACTIVE YES /home/oracle/app/oracle/oradata/orcl/redo02.log 2 CURRENT NO /home/oracle/app/oracle/oradata/orcl/redo02b.log 2 CURRENT NO /home/oracle/app/oracle/oradata/orcl/redo03.log 3 INACTIVE YES /home/oracle/app/oracle/oradata/orcl/redo03b.log 3 INACTIVE YES
Delete all members of redo log group 1 and kill your instance.
[oracle@localhost ~]$ rm /home/oracle/app/oracle/oradata/orcl/redo01* [oracle@localhost ~]$ ps -ef |grep smon oracle 8176 1 0 06:44 ? 00:00:03 ora_smon_orcl oracle 9057 3164 0 08:10 pts/5 00:00:00 grep smon [oracle@localhost ~]$ kill -9 8176
Try to open your database …
SQL> startup ORACLE instance started. Total System Global Area 456146944 bytes Fixed Size 1344840 bytes Variable Size 385878712 bytes Database Buffers 62914560 bytes Redo Buffers 6008832 bytes Database mounted. ORA-03113: end-of-file on communication channel Process ID: 9184 Session ID: 17 Serial number: 7
look at your alert log
... ORA-00313: open failed for members of log group 1 of thread ORA-00312: online log 1 thread 1: '/home/oracle/app/oracle/oradata/orcl/redo01.log' ORA-00312: online log 1 thread 1: '/home/oracle/app/oracle/oradata/orcl/redo01b.log' USER (ospid: 9184): terminating the instance due to error 313 ...
Start your database in MOUNT mode
SQL> startup mount ORACLE instance started. Total System Global Area 456146944 bytes Fixed Size 1344840 bytes Variable Size 385878712 bytes Database Buffers 62914560 bytes Redo Buffers 6008832 bytes Database mounted.
Query the V$LOG view
SQL> select member, a.group#, a.status, b.status, a.archived from v$log a, v$logfile b where a.group# = b.group# order by a.group#, member; MEMBER GROUP# STATUS STATUS ARC ------------------------------------------------------------ ---------- ---------------- ------- --- /home/oracle/app/oracle/oradata/orcl/redo01.log 1 INACTIVE YES /home/oracle/app/oracle/oradata/orcl/redo01b.log 1 INACTIVE YES /home/oracle/app/oracle/oradata/orcl/redo02.log 2 CURRENT NO /home/oracle/app/oracle/oradata/orcl/redo02b.log 2 CURRENT NO /home/oracle/app/oracle/oradata/orcl/redo03.log 3 INACTIVE YES /home/oracle/app/oracle/oradata/orcl/redo03b.log 3 INACTIVE YES
The redo log group 1 is INACTIVE and ARCHIVED so simply issue the following command:
SQL> alter database clear logfile group 1; Database altered.
Open your database
SQL> alter database open; Database altered.
If you are in the situation to have lost an INACTIVE and NOT already ARCHIVED redo log group then your command should be the following:
SQL> alter database clear unarchived logfile group 1; Database altered.
Next step is to perform a complete backup
RMAN> backup database;
Thank you for giving your valuable time to read the above information.
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