LGWr writes when:
1)at commit
2)when 1/3rd full
3)when there is 1mb of redo
4)every 3 seconds
5)before DBWn writes.
The LGWR writes redo log entries into an on-line redo log file when
1. transaction is committed.
2. More than 1 MB of redo log buffer enteries.
3. 1/3 of the redo log buffer is full.
4. Every 3 seconds.
