Search notes:

v$log

v$log contains information about each log group

The individual log files and their group membership is recored in V$logfile.

status

Common values for the status column are:

UNUSED: Oracle has never written to this group,
CURRENT: This is the active group.
ACTIVE: Oracle has written to this log before, it is needed for instance recovery. The active log is the one with the current log sequence number
INACTIVE: Oracle has written to this log before; it is not needed for instance recovery.

See also

SQL statement alter database

Oracle Dynamic Performance Views