Re: Redo group members - are they written to in parallel?

Actually it depends on OS' ability to do Asinc (or List) I/O. Previuos Solaris versions supported it only for raw devices. Oracle's LGWR (as well as DBWR) tries to make request to OS to write in parallel. This can be seen as 'log file parallel write' in V$SESSION_WAIT, V$SYSTEM_EVENT or V$SYSTEM_EVENT.

On my AIX4.2 box all mirrored log files do have the same timestamps.

Albert

--
Albert Balbekov, Senior Consultant
GRT Inc.

  Andrew Babb <andrewb_at_mail.com> wrote:
> Back in the days of Oracle7 v7.1, I was implementing a 7x24 system, and we did
> some testing on Redo Log Members.
>
> When the members were on File Systems, and could not take advantage of Async
> I/O, the time to write to 2 Members over that of one member was approx 2.1 :
1.
>
> When we put the Redo Logs on RAW Devices, and thereby enabled Async I/O the
> write times went to approx 1.1 : 1.
>
> When I spoke to Oracle, they confirmed that the writes were infact done
> Serially.
>
> I am not sure what the rules are in Oracle8, but the way I tested was to just
> create a very large insert loop and timed the execution.
>
> Hope this helps,
> Andrew
>
> Rob Bailey wrote:
>
> > The question is in the subject - I have observed the last update times of
> > redo log members and they dont seem to be in seqence - does anyone know for
> > sure if they are written to in parallel?
> >
> > Or am I just wrong?
>
>

-----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own Received on Mon Apr 12 1999 - 16:59:26 CDT