Lost Online redo logs after shutdown

There wouldn't be any data loss, as a graceful shutdown triggers DBWR to flush dirty blocks to be written to corresponding datafiles.

After mounting the database, recovery has to be performed to inform Oracle that incomplete recovery has been performed and the database can be opened with resetlogs option.

1. Connect with sample user and insert some records, commit the transaction and shutdown the database

2. Mount the database and remove redo log files

3. Initiate a dummy incomplete recovery inorder for Oracle to allow us to open with resetlogs option

SQL> alter database recover automatic using backup controlfile until cancel;

SQL> recover cancel;

SQL> alter database open resetlogs;

Oracle will not actually do any recovery but try to apply the archive log that is not yet generated, below is the image from alert log file

4. Why can't I just mount the database and open with resetlogs option if no recovery is required

Oracle will only resetlogs only after incomplete recoveries, though there is no data loss in some cases like if present control file is lost or in this case. Below is the error we receive if we try to open with resetlogs after mounting the database

So, losing online redo log files will have data loss in all the cases but not in the case when they are loss after graceful shutdown.

That's it!!!

Regards

Charan