I know you know what will happen if you lost one or all your online redo files. Always multiplex your Redo logs (controlfile too) and store it several partitions. So, one of student did not it and requested to me what to do. For him I prepare this tutorial.:) If your Redo log files are multiplexed and you lost one of the member of redo file do not panic, just copy another member of same group and paste it with lost member place. Suppose you have 3 groups (redo1, redo2, redo3) and all group has three members (redo1a, redo1b, redo1c, ...) If you lost redo1a.log just take redo1b.log and copy it where should be redo1a.log and do not forget to rename it to redo1a.log. /u01/oradata/mydb/ redo1a.log redo2a.log redo3a.log /u02/oradata/mydb/ redo1b.log redo2b.log redo3b.log /u03/oradata/mydb/ redo1c.log redo2c.log redo3c.log If your redo logs were not multiplexed and you lost redo files then follow me: [oracle@localhost ~]$ hostname localhost....