Re: Oracle Data Guard

With TCP over standard ethernet the maximum transfer unit (MTU) is about 1500 bytes, this means if you want to send 2000 bytes over network, you have to fragment it in 2 packets and send them separately. This means double packet headers, double latency etc. Jumbo frames is a capability of some Gbit ethernet cards which allow them to transfer about 9000 bytes in a single packet. SDU is session level transfer unit (session data unit). When you enable jumbo frames and set MTU/SDU to 8192 for example, you'll fit much more in single packet, thus increasing performance for larger transactions.

Also make sure that TCP.NODELAY is unset in your sqlnet.ora or is set to true.

More info can be found from:

http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96653/troubleshooting.htm#635905

Tanel.

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Monday, December 08, 2003 11:49 PM

> Hi,
>
> Tanel,
>
> "enabling jumbo frames and SDU size if using
> Gbit ethernet,"
>
> can you elaborate on this?
>
>
>
>
> -----Original Message-----
> Sent: Monday, December 08, 2003 1:34 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Hi Tanel,
>
>
> Much appreciated, The fact is I am interested in
> Logical standby rather than physical.
>
> Our 30-50% of our Production data needs to be
> replicated to another database and where they will
> have their processing and batches.
>
> Now We didn't go to Snapshot because It is on
> multiple tables (where we didnot have PK's and many
> tables) and due to performance issue I didn't want to
> use Snapshots (they did not want any tables to be
> truncate before being loaded even via snapshots).
>
> The best option I think is Logical Standby Database.
> Or Can you please suggest me any other means.
>
> Replication should be quicker like once in
> every 20 minutes, Even Transportable tablespacs does
> not work here since they need all tables to 24*7.
>
> Any suggestion would be more helpful.
>
> with thanks,
> Vi.
>
>
>
> --- Tanel Poder <tanel.poder.003_at_mail.ee> wrote: > >
> Hi All,
> > >
> > > can any one let me know kindly the following info.
> > >
> > > 1) Has any one used the Oracle 9i Data Guard?
> >
> > Yes, physical standby and successfully.
> >
> > > 2) If yes then, is there any performance impact
> > on
> > > Target/Source server database.
> >
> > Your database has to be in archivelog mode, but when
> > you are thinking such
> > solutions as DG, then you probably are already
> > running archivelog anyway.
> >
> > If you run in maximum protection or maximum
> > availability, yes there is. The
> > impact depends mainly on network connection between
> > primary and standby(s)
> > and the speed of redolog disks. You could tune these
> > by using faster
> > network, enabling jumbo frames and SDU size if using
> > Gbit ethernet, also
> > setting lgwr and log apply processes priority higher
> > than others.
> >
> > > 3) any drawbacks using Data Guard.
> >
> > You should set your database or critical tablespaces
> > to force logging mode
> > in order to transfer all changes to standby in
> > physical standby. That means,
> > performance improvements which take advantage of
> > nologging operations (such
> > insert append nologging etc), will not run that fast
> > anymore.
> > In logical standby, I think there's no such
> > requirement, but I don't
> > recommend you to use logical stby yet, it's more
> > like a prototype currently,
> > not exactly a working product.
> >
> > Tanel.
> >
> >
> > --
> > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.net
> > --
> > Author: Tanel Poder
> > INET: tanel.poder.003_at_mail.ee
> >
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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