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2 Replies Latest reply: Oct 24, 2012 7:12 AM by Omega3 RSS

Creating DB service in 3 node RAC

Omega3 Newbie
Currently Being Moderated
GI and DB Version: 11.2.0.3

We have a 3-node RAC. We have around 15 applications connecting to 25 different schemas in this DB. For each application , we create a RAC DB service. Should we be adding 2 instances as the preferred instance or 1 preferred instance and 2 available instance ?
Which one is recommended
srvctl add service -d ORCL -s GRN_SV -r ORCL1,ORCL2 -a ORCL3

or

srvctl add service -d ORCL -s GRN_SV -r ORCL1 -a ORCL2,ORCL3
A related question:
Do you guys add any other parameters (like BASIC, PRECONNECT, ....etc ) for service creation as mentioned in the below documentation ?

http://docs.oracle.com/cd/E11882_01/rac.112/e16795/srvctladmin.htm#i1008562
  • 1. Re: Creating DB service in 3 node RAC
    Sebastian Solbach (DBA Community) Guru
    Currently Being Moderated
    Hi,

    that depends on what you want to achieve.

    If a service runs on 2 instances (command 1), then already the connections from the first client will be distributed over the 2 instances.
    If a service runs only on one instance (command2), then all connections of the clients will be going to the same instance.

    If instance 1 fails, then the szenario's will be as follows:

    1.) Only 50% of the users will recognise the failure and TAF will only be applicable to 50% of the users. The users connected on instance 2 will not be affected at all (nearly... there may be a small performance impact due to reconfiguration).
    2.) All users will be affected. But TAF will fail over all sessions to the new instance (which can either be ORCL2 or ORCL3)

    Have a look at this paper:
    http://www.oracle.com/technetwork/products/clustering/overview/awm11gr2-130711.pdf

    Regards
    Sebastian
  • 2. Re: Creating DB service in 3 node RAC
    Omega3 Newbie
    Currently Being Moderated
    Thank you Sebastian.

    You said:
    +1.) Only 50% of the users will recognise the failure and TAF will only be applicable to 50% of the users. The users connected on instance 2 will not be affected at all (nearly... there may be a small performance impact due to reconfiguration).+

    Because of what you've mentioned above (in Italics ) To give maximum availability to the clients , it looks like option 1
    srvctl add service -d ORCL -s GRN_SV -r ORCL1,ORCL2 -a ORCL3
    is better

    Do you guys add any other parameters (like BASIC, PRECONNECT, ....etc ) for service creation ?

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