I have a 12c DB running in noarchivelog mode that has had ALL redo log directories covered up when a filesystem was mounted over them.
Net effect was DB unable to write to ANY redo logs.
Filesystems were unmounted and I subsequently have DB that was busy at the time which will not start.
Database mounts but will not start...
getting:
ORA-00742: Log read detects lost write in thread 1 sequence 10637 block 21271
ORA-00312: online log 2 thread 1:
'/LUN02/app/oracle12/oradata/redob/lawp/lawpredo2b.log'
Have tried recover until cancel and open resetlogs without success.
also dumped and validated redo logs and cleared the logfile group to per My Oracle (metalink) doc without success.