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Dedicated server VS Shared Server [message #290169] Thu, 27 December 2007 21:53 Go to next message
trantuananh24hg
Messages: 668
Registered: January 2007
Location: Ha Noi, Viet Nam
Senior Member
Hi all!

Recently, I have many connections (virtual circuit) from an application, and I realize that, the machine inwhich Oracle Database configured as Dedicated Server. I know that, using the Dedicated server useful than MTS, many guides, many advices such as ..

TomKyte


When should I consider using the MTS?

Of course, your mileage may vary, but most Oracle experts agree that the MTS is only used in very rare cases, primarily for instances with resource limitations or a high "think time". Let's take a closer look at the rules-of-thumb for using Oracle shared servers. In this case study by Brian Keating we see that his case study results do not recommend using the multi-threaded server (MTS) if there is sufficient RAM on the Oracle server:

If there is enough physical memory on the server so that all of the concurrent processes (operating system, Oracle, user connections, applications, etc.) during peak periods can fit into physical memory, then don’t bother implementing MTS. There are two reasons for this:

As long as you do not use more than 100% of the physical memory on a server, the operating system will not have to page or swap. If that’s the case, there will not be any pressing need to conserve memory. In other words, reducing a system’s memory usage from 80% of physical memory to 20% of physical memory will not really buy you anything—it will simply mean that more of your physical memory will be idle most of the time. So, unless you have at least some virtual memory usage, I would not recommend going through the additional complexity of MTS.


More importantly, MTS appears to cause some additional CPU overhead as compared to running an equivalent number of dedicated connections. Therefore, if a system is CPU-bound, then MTS will probably not be a good option for that system.
Keating also notes cases where using the multithreaded server (MTS can cause a degradation in performance:

I encountered one situation in which a database server’s CPUs were constantly pegged at 100% usage, and the CPU queue length (the number of processes waiting for CPU time) was typically 6 or 7 during peak periods. That database had been using MTS for several years, even though there was more than enough physical memory on the system to support dedicated connections. So, in an attempt to reduce the system’s CPU usage, I disabled MTS. The average CPU queue length during peak periods went down to about 4.

Moral of the story: If a system is CPU-bound and that system has enough RAM to fit all of its processes into physical memory, then MTS should probably not be used on that system.



Every day, about 1000 connections maximum are created througout an application Java, and I am considering to change the machine from Dedicate to Shared server.

Would you like to send me some advice?

Thank you!

Re: Dedicated server VS Shared Server [message #290172 is a reply to message #290169] Thu, 27 December 2007 22:06 Go to previous messageGo to next message
BlackSwan
Messages: 25050
Registered: January 2009
Location: SoCal
Senior Member
There are 84600 seconds per DAY.
Your 1000 connections every day is one connection per 84 seconds;
more than 1 minute elapses between connection request.

Again MTS is beneficial potentionally was the number of existing SESSIONS increases & has little to do with connection RATE.

IMO, this is NO excuse for going to MTS.

Again, IMO, effort would be better spent developing JAVA connection pooling and driving the effective new connections toward ZERO between database restarts.

I supported a single production Oracle database server system that sustained 1800+ concurrent connections across normal business hours using dedicated connections which performed measurably better than using MTS.

We started off with under horse powered system (too few CPUs & not enough RAM) using MTS.
After getting onto a system with sufficient resources & switching to Dedicated Server, performance measureably improved.

[Updated on: Thu, 27 December 2007 22:30] by Moderator

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Re: Dedicated server VS Shared Server [message #290255 is a reply to message #290172] Fri, 28 December 2007 03:46 Go to previous message
trantuananh24hg
Messages: 668
Registered: January 2007
Location: Ha Noi, Viet Nam
Senior Member
Oh, thank you Anna! You make me more clarifing!

The Database which I support and monitor daily, has only 1000 connection maximum, and not concurrency. Before your answer, I've been being wondered about the MTS.

Happy new year, Michel and Anna!

Take a bit spelling with Vietnamese :"Chuc suc khoe va hanh phuc". Very Happy
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