CURRENT state means that redo records are currently being written to that group. It will be until a log switch occurs. At a time there can be only one redo group current.

If a redo group containing redos of a DIRTY buffer that redo group is SAID to be ACTIVE state. As we know log file keep changes made to the data blocks then data blocks are modified in buffer cache (dirty blocks). These dirty blocks must be written to the disk (RAM to permanent media).

And when a redo log group contains no redo records belonging to a dirty buffer it is in an "INACTIVE" state. These inactive redo log can be OVERWRITTEN.

One more state UNUSED initially when you create new redo log group its log file is empty on that time it is unused. Later it can be any of the above mentioned state.

CURRENT state means that redo records are currently being written to that group. It will be until a log switch occurs. At a time there can be only one redo group current.

If a redo group containing redos of a dirty buffer that redo group is said to be ACTIVE state. As we know log file keep changes made to the data blocks then data blocks are modified in buffer cache (dirty blocks). These dirty blocks must be written to the disk (RAM to permanent media).

And when a redo log group contains no redo records belonging to a dirty buffer it is in an "INACTIVE" state. These inactive redo log can be overwritten.

One more state UNUSED initially when you create new redo log group its log file is empty on that time it is unused. Later it can be any of the above mentioned state.