Re: sdu, send/recv buffers, etc.

From: Stefan Koehler <contact_at_soocs.de>
Date: Thu, 11 Feb 2016 20:32:59 +0100 (CET)
Message-ID: <1768262170.653824.1455219180000.JavaMail.open-xchange_at_app02.ox.hosteurope.de>



Hi Patrice,
the last mentioned blog post is mine - so maybe i can share something :)

> Has anyone seen major improvements by tweaking these parameters for WAN links?
  

Yes, in case of "large" data streams - one of the best examples for this would be the redo stream by Data Guard. Oracle also published some results in its MAA white papers, e.g. here on page 10: http://www.oracle.com/au/products/database/maa-wp-10gr2-dataguardnetworkbestpr-134557.pdf

> We're serving Oracle Forms over WAN and some user sessions were seeing disconnections. After tweaking networking settings the disconnections seem to
> have stopped, but performance hasn't improved all that much.​ At least... one user told me he saw no performance improvement.

Before tweaking any network parameters you should analyze if the end user is suffered by any corresponding waits at all. This is what i tried to show in my blog post. Oracle SDU (and OS network buffer) issues are not very common in classic form apps as the amount of transferred data is usually not that huge (exceptions prove the rule). It is also possible that one user is affected and the other is not (depending on the business process and actions they execute), so you really have to measure and interpret the diagnostic data first. In your described user case it seems like network time is not a huge contributor to response time.

Hope this helps a bit.

Best Regards
Stefan Koehler

Freelance Oracle performance consultant and researcher Homepage: http://www.soocs.de
Twitter: _at_OracleSK

> Patrice sur GMail <patrice.boivin_at_gmail.com> hat am 11. Februar 2016 um 19:50 geschrieben:
>
> Last week I looked on the 'net for recommendations on these.
> Clear as mud. Often the values people quote in the forums or on their blogs doesn't mention what network throughput they have, or even the
> operating system they're running on.
>
> Same lack of precision on the multiple web pages mentioning Windows registry settings to tune tcp/ip on WAN networks: Almost none of them mention
> what version of Windows they are talking about or what throughput they have. I can't remember finding one that showed statistics before and after.
> I am a bit leery because pre-Y2K I tried using RAW partitions on Windows and discovered it made zero performance difference.
>
> Oracle set SDU max size to 65535
> On Ethernet though it's more useful to set it to 32120, right?
>
> ​There is a blog page which tracks down some confusion in one of Oracle's own tech note pages, which ended up being replicated on dozens of Oracle
> DBAs' blog pages. SDU ought to be a multiple of the MSS, not the TDU. MSS on Ethernet is 1460.
> ​
> (ref. This DBA blog (5/6th of the way down)
> http://khalidthedba.blogspot.ca/
> ​ )​
> ​
>
> The send and recv buffer sizes depend on the round trips, OakTable mentions x1 but as of 10g I saw x3 being used. x Mbps throughput / 1000000 x
> round trip ms / 1000 x 3 ? Hopefully your network doesn't have full-duplex half-duplex mismatches.
> ​
> Has anyone seen major improvements by tweaking these parameters for WAN links?
> We're serving Oracle Forms over WAN and some user sessions were seeing disconnections.
> After tweaking networking settings the disconnections seem to have stopped, but performance hasn't improved all that much.​ At least... one user
> told me he saw no performance improvement.
>
> ​This thread shows some improvement, in that larger SDU sizing reduced the amount of "more data to client". I used to see that as well but now
> it's gone.
> http://scn.sap.com/community/oracle/blog/2013/02/07/oracle-sqlnet-researching--setting-session-data-unit-sdu-size-and-how-it-can-go-wrong
>
>
> -- Patrice
>
> My profiles: [Facebook] <http://www.facebook.com/home.php?#!/profile.php?id=100000206805521> [LinkedIn]
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>

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Received on Thu Feb 11 2016 - 20:32:59 CET

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