Redo Log buffers are written to disk when the following 4 things happen:

1. a commit occurs.
2. redo log buffer becomes 1/3rd full.
3. DBWR completes cleaning the buffer blocks as during a checkpoint.
4. A LGWR time-out occurs (every 3 seconds)

My question is if the timeout occurs every 3 seconds wouldn't that be the primary trigger for the LGWR to write to the disks.

Am I completely missing the idea here?

Thanks