Hi,

Make sure that the device in which the logfile is stored is available.
If it is temporarily not available, correct the problem, and re-start the database.
NO RECOVERY is required.

Alternatively if your device is permanently out of use then,

(I am under the assumption that the database is closed normally).

1. Mount the database.
2. Drop the unavailable redo log group.
3. Open the database.

Vijay.