Re: Lamport vs Broadcast on Commit - RAC only

Platform is 9.2.0.6/RHAS 3.0.  

Insert/update performance is unknown at this point - new application and I'm just getting pulled into the project - another DBA has been the primary contact. I'll have a better idea of performance characeristics of the app once I meet with the development team today.  

Thanks - Brian

K Gopalakrishnan <kaygopal_at_gmail.com> wrote: Brian:

You have not mentioned the version and platform. So I assume it is 9iR2 and some flavor of UNIX other than Tru64. Please correct me otherwise, as the results vary on 10gR2 and Tru64.

Broadcast on Commit is certainly expensive. But I have not seen very noticeable performance overhead on BOC in our benchmarks. Others say the overhead is around 5-10%. Recently I had seen one case where the top wait was 'wait for scn from all nodes' when BOC is used. You don't need to worry much unless you are seeing huge waits for 'wait for scn' wait. Packaged Applications (Oracle Ebusiness suite or SAP) require MCPD as 0 to force BOC SCN propagation.

Starting from 10gR2 BOC is the default method for SCN propagation as they have change LGWR to asynchronous.

CC: racdba-s: Do you guys have any comments?

Regards,
Gopal

On 7/26/05, Brian Wisniewski
wrote:
> Has anyone done testing using the lamport vs broadcast on commit scheme and
> can comment on the results?
>
> We have an application where we're needing to use the broadcast on commit
> due to the way the application was designed. I'm curious as to what type of
> performance hit will be associated with it. Oracle's defines the hit as
> "marginally more resource intensive" but somehow I'm not all warm and fuzzy
> with that definition.
>
> I'm want to run some tests to try and determine the impact but just don't
> have the time right this moment. I'd appreciate feedback from anyone who's
> tested this and would be willing to share their results.
>
> Thanks - Brian
>
>
>
>
>
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-- 
Best Regards,
K Gopalakrishnan 
Co-Author: Oracle Wait Interface, Oracle Press 2004
http://www.amazon.com/exec/obidos/tg/detail/-/007222729X/
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