Re: Using dblinks over distance
Date: Fri, 10 Jan 2020 16:19:01 +0000
Message-ID: <LNXP265MB15624066D692C537D1E0C550A5380_at_LNXP265MB1562.GBRP265.PROD.OUTLOOK.COM>
I'm not going to argue about the latency/bandwidth thing, but I have to say that one of the things I learned in physics classes about 50 years ago was that when you caused an electric current to flow the "flow" was virtually instantaneous but if you were running the current through a cable across the Atlantic it would take about 100 years for any individual electron to get from one side to the other. (Just like a Bugatti Veyron won't be able to get round the M26 (London Orbital) in 26 minutes at 5:00 pm on Friday afternoon - only more so)
Regards
Jonathan Lewis
From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on behalf of Clay Jackson (cjackson) <Clay.Jackson_at_quest.com> Sent: 10 January 2020 16:07
To: knecht.stefan_at_gmail.com; vishal_at_vishalgupta.com Cc: Mladen Gogala; oracle-l-freelists
Subject: RE: Using dblinks over distance
Let’s not confuse latency (how long it takes one electron to get from one end of the pipe to the other, usually expressed in some fraction or multiple of seconds) with bandwidth (how many “thingies” can I move from one end of the pipe to the other in some period of time, usually expressed in bits per second).
Both contribute to making a network (any network, not just local or wide-area) APPEAR either fast or slow. The latter (bandwidth) is something that is almost completely controllable (just add money). The former (latency) is usually a VERY small component of the overall “business application response time”, since light moves at 300 MILLION meters per second (and electrons only a bit slower). But, as the saying goes, “The speed of light isn’t just a good idea, it’s THE LAW”; so, in any network involving connection spanning 10K KM or more, latency will be a larger component..
I think there have already been a few suggestions on how to mitigate latency (like local materialized views) and, as I said, bandwidth is just a question of “How big is your checkbook?”.
Clay Jackson
Database Solutions Sales Engineer
clay.jackson_at_quest.com<mailto:clay.jackson_at_quest.com>
office 949-754-1203 mobile 425-802-9603
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From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> On Behalf Of Stefan Knecht
Sent: Thursday, January 9, 2020 11:42 PM
To: vishal_at_vishalgupta.com
Cc: Mladen Gogala <gogala.mladen_at_gmail.com>; oracle-l-freelists <oracle-l_at_freelists.org>
Subject: Re: Using dblinks over distance
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Not really. If you are going over the internet, regardless of your connection speed, you will hit bottlenecks due to the competition will millions of others (across a 1000 miles). What Mladen is referring to is purchasing dedicated bandwith between the 2 locations, and thus, getting far more guaranteed speeds and latency.
On Fri, 10 Jan 2020, 02:40 Vishal Gupta, <vishal_at_vishalgupta.com<mailto:vishal_at_vishalgupta.com>> wrote: Problem of slow response over database link to a database situation at 1000+ miles distance is indeed distance (i.e. network latency), not speed.
Regards,
Vishal Gupta
From: <oracle-l-bounce_at_freelists.org<mailto:oracle-l-bounce_at_freelists.org>> on behalf of Mladen Gogala <gogala.mladen_at_gmail.com<mailto:gogala.mladen_at_gmail.com>>
Reply-To: <gogala.mladen_at_gmail.com<mailto:gogala.mladen_at_gmail.com>>
Date: Thursday, 9 January 2020 at 18:41
To: <oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>>
Subject: Re: Using dblinks over distance
The problem is not the distance, the problem is the network speed. WAN is usually slightly slower than 10Gb LAN. Thus the solution: improve the network speed. Buy more dedicated lines from your network provider. Also, it's about the application design: you shouldn't do real time queries against the database in the server room far, far away. You should use materialized views and cache the data locally. It's called "intelligent design". On 1/9/20 1:27 PM, Cohen, Andrew M. wrote: As we move some of our database VMs to the cloud we have come across the following situation where the database links between databases (which used to be all on prem) are now being attempted over thousands of miles. This has caused extremely poor performance. We have found that an arraysize session parameter assists with some of the select statements, but updates which use links to get data don’t seem to perform any better with this arraysize parameter. To make matters more complicated, we are making these calls in PeopleSoft applications.
We’re using Oracle 18 and 19 databases on Rhel 7 mostly.
Does anyone have any suggestions as to how to improve performance using database links over distance?
Thanks,
Andy
-- Mladen Gogala Database Consultant Tel: (347) 321-1217Received on Fri Jan 10 2020 - 17:19:01 CET
-- http://www.freelists.org/webpage/oracle-l
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