Re: LGWR vs DBWn

Hi!

Backgroup process LGWR writes changes from buffer to file. Server (shadow) processes are the ones which put change vectors to log buffer before they make any change to a datablock in buffer. Also note that if a change requires generation of rollback, then first rollback entries have to be created, which means that first overall we have to write change vectors for rollback entries to log buffer, then change blocks in rollback segment, then write change vector of data block to log buffer and then modify the data block itself..

Server processes are also responsible for reading data blocks from disk to memory, modify them in buffer cache, but under normal circumstances they don't write any blocks to disk. DBWR does the job.

Note that according Oracle terminology, user process is the sqlplus, oci library or client on your desktop, server process (shadow process) is the one which serves you on Oracle side and background processes are the ones which you don't directly interfere with, such are LGWR and DBWR..

Tanel.

"Peter" <peter_at_nomorenewsspammin.ca> wrote in message news:1j3qev8db8aht7eob03lnc2ug1qt3mt4m2_at_4ax.com...
> If it is the LGWR that writes the redo logs into the redo log buffer
> then what writes the redo logs into the redo log files? A system
> process?
> If it is the user process that writes the datablocks into the db
> buffer cache, then what writes those dirty data buffers into the the
> datafiles? Is it the DBWn?
>
> Thanks
>
Received on Sun Jun 15 2003 - 20:10:38 CDT