Oracle Database Discussions

Hi All,

I am a bit confused about the working of DBW0 and LGWR processes.

"A checkpoint performs the following three operations:
Every dirty block in the buffer cache is written to the data files. That is, it synchronizes the datablocks in the buffer cache with the datafiles on disk.
It's the DBWR that writes all modified databaseblocks back to the datafiles. "

I know this is very basic question and have read many documents about this.
But my question is,if DBW0 itself writes the blocks to disk(datafiles) then what is the task of LGWR ( writing from redo log buffer to online redo log and then to datafiles).Online redo logs will store all modified (committed) redo records and will flush the contents to datafile at some interval.Then isnt the same task performed by DBWR???

Thanks,
Aashish S.