7 Replies Latest reply: Jan 19, 2012 3:50 AM by Billy~Verreynne RSS

    Memory and CPU load for one Oracle instance

    911314
      I need to design a database server with 5 oracle instances.
      Each instance have only 2 or 3 connected application users and the rate of transactions is about 10 transactions/hour.

      How can I estimate to total memory and CPU needed for my server ?

      The minimum esimation : 2x2Ghz and 2Go of RAM per instance is it pertinent ?

      Dominik
        • 1. Re: Memory and CPU load for one Oracle instance
          asifkabirdba
          Seems OK.


          Regards
          Asif Kabir
          • 2. Re: Memory and CPU load for one Oracle instance
            819493
            Hi,

            I guess that the correct answer to this question is "it depends"...

            It's very hard to estimate the correct system resources that the instances will need from the supplied information only. It depends on the amount of data, the operating system, the characteristics of the database load etc.

            Is this a consolidation of 5 old database servers? Or is it 5 new instances that will be taken into production?
            Would it be possible to instead create one instance, but with 5 different schemas?

            HtH
            Johan
            • 3. Re: Memory and CPU load for one Oracle instance
              911314
              Thank Johan, but each application must have a separate instance, it's a pre-requisite.
              • 4. Re: Memory and CPU load for one Oracle instance
                sb92075
                908311 wrote:
                Thank Johan, but each application must have a separate instance, it's a pre-requisite.
                I suggest that sum of all 5 SGA equal about 0.75 of total RAM in the system
                • 5. Re: Memory and CPU load for one Oracle instance
                  819493
                  Hi,

                  Is this a consolidation of 5 old database servers? Or is it 5 new instances that will be taken into production?

                  If it is a consolidation, I'd start off with the same amount of memory allocation for each instance, and then tune it, so that each instance will have as optimal memory allocation as possible.
                  And that the total allocation corresponds to roughly 75% of the hardware RAM (a bit depending on what os you're running)

                  If this is a new system, with 5 new instances, I guess that your estimate is as good as any. Personally, I'd do as when brewing tea, add one for the pot... ;-)

                  5x 2 CPU = 10 CPU => 4x quad-cpu
                  5x 2 GB RAM + some for the os => 24 - 32 GB RAM, or 16GB minimum.

                  It's better to add a bit extra when estimating the system, since if the managers won't give you what you want, if it gives you bad performance, you can always blame them for not buying the hardware you wanted... :-)

                  HTH
                  Johan
                  • 6. Re: Memory and CPU load for one Oracle instance
                    Aman....
                    Dominik wrote:
                    I need to design a database server with 5 oracle instances.
                    Each instance have only 2 or 3 connected application users and the rate of transactions is about 10 transactions/hour.

                    How can I estimate to total memory and CPU needed for my server ?

                    The minimum esimation : 2x2Ghz and 2Go of RAM per instance is it pertinent ?

                    Dominik
                    Though the picked specs look okay but the better answer, as being mentioned already, would be "it depends" . At this moment, almost all the machines are coming with very good specs so 2gb probably would be the least . You can even have a 4gb RAM system with x86_64 architecture , leaving room for future growth if needed. About setting the memory for the SGA, if the release is 11g, setting the Memory_Target would take care of the the memory allocation for both SGA and PGA and you can start by the default that Oracle picks which I guess is about 40% of the total RAM. Afterwards, you can monitor the performance and can bring down the memory settings if you feel its overly allocated.

                    That said, I think that this is a question better answered by the capacity planning and management people. I shall see if I can ask my friend, who is in this domain to comment on it.

                    Just my 2 cents.
                    Aman....
                    • 7. Re: Memory and CPU load for one Oracle instance
                      Billy~Verreynne
                      Dominik wrote:

                      but each application must have a separate instance, it's a pre-requisite.
                      Why? Running different applications against the same instance is often the norm.

                      Running 5 instances on a single server however is not. Oracle scales by adding MORE servers to a SINGLE database. It is called Oracle RAC.

                      You want to add MORE databases to a SINGLE server. The exact opposite.

                      So what are your justifications for this exception? And why not use 5 separate servers if 5 instances are needed? Why not use cloud computing if you want to use the h/w layer as multiple servers? Exactly what business requirements need to be met?