Recover From Missing Redo Log Files

The disk that is holding the most up-to-date redo log files experienced a fatal failure, and the database wouldn`t come up any more. It complains about missing redo logs. So, you copy the redo log files from a recent backup; but still the database won`t come up with error messages like ORA-00314: log 1 of thread 1, expected sequence# doesn`t match.

SQL> startup
ORACLE instance started.
Total System Global Area 4294967296 bytes
Fixed Size 1306568 bytes
Variable Size 2534150200 bytes
Database Buffers 1728053248 bytes
Redo Buffers 31457280 bytes
Database mounted.

ORA-00314: log 1 of thread 1, expected sequence# doesn't match
ORA-00312: online log 1 thread 1: '/opt/oracle/oradata_4/RedoLogFiles/log1.dbf'

How to bring up the database with no redo logs?

In production environments, usually archive logging will be turned on. If that's the case, consult the Oracle system administration documentation to restore the lost transactions.

In all other cases it is very unlikely to recover the lost transactions. So the easiest way to bring up the database is to rebuild the control file. The steps to rebuild the control file with new redo log files are as follows:

Start the database up.

SQL> startup <- let it complain about online redo log

Run the following command to dump the control file into a trace file.

SQL> alter database backup controlfile to trace;
Database altered.

Go to udump location and locate the file which contains the necessary SQL text to build the control file. The easiest way is to grep for text like `CREATE CONTROLFILE REUSE DATABASE`. Once you locate the trace file, change the extension from trc to sql and change NORESETLOGS to RESETLOGS. That is, a SQL like:

CREATE CONTROLFILE REUSE DATABASE "XYZ" NORESETLOGS NOARCHIVELOG

should be changed to

CREATE CONTROLFILE REUSE DATABASE "XYZ" RESETLOGS NOARCHIVELOG

Shut down the database

Run the script that you just modified -- it creates a new control file.

Open the database with

alter database open;

You may have to read the alert messages carefully and act accordingly to fix the things up, if the database won`t come up even after the above step.

Finally bring down the database and bring it up as you usually do.