Re: "gc current block busy" wait in Concurrent BATCH Processes Run

gc means global cache, which means it's cache fusion/interconnect related.

More than likely you have processes on both/all nodes of the cluster writing
to the same table(s) and cache fusion is having trouble keeping up with the
communication of which blocks are dirty (and sending the data back and
forth) and which are not.

In my experience with RAC, if you have a lot of writes to a set of tables
you're much better off localizing all those connections on one node so you
don't have the "gc" wait events. Throughput goes up as well.

Not exactly what Oracle is marketing when they talk about RAC, but that has
been my experience.

Finn


On 2/13/08, VIVEK_SHARMA <VIVEK_SHARMA@xxxxxxxxxxx> wrote:
>
>
> Folks
>
> In a Benchmark Run, 256 concurrent BATCH Processes on RAC using Dedicated
> Sessions (NON-MTS) showing the following Waits:-
>
> How is the "gc current block busy" wait to be addressed?
> From the Statspack Report (Level 7) which section gives the Objects which
> is incurring this wait? Is it the "Segments By Current Blocks Received"
> section OR the "Segments by CR Blocks Received" section?
>
> Will share the Statspack Report, as needed.
>
> Config:-
> Oracle 10.2.0.3 on 3 Node RAC
> Solaris 10
>
> Cheers
>
> Vivek
>
> Statspack Report's Time Elapsed: 11.97 (mins)
>
>
>
> Top 5 Timed Events
> Avg    %Total
>
> ~~~~~~~~~~~~~~~~~~
> wait    Call
>
> Event                                     Waits        Time
> (s)    (ms)    Time
>
> ----------------------------------------- ------------ ----------- ------
> ------
>
> CPU time                                                 5,854
> 57.6
>
> gc current block busy                     24,910         1,463      59
> 14.4
>
> SQL*Net break/reset to client          1,075,218         1,285       1
> 12.6
>
> gcs log flush sync                       103,520           511
> 5      5.0
>
> gc buffer busy                             6,489
> 367      57      3.6
>
> -------------------------------------------------------------
>
>
>
> Host CPU (CPUs: 120)
>
> ~~~~~~~~ Load Average
>
> Begin End User System Idle WIO WCPU
>
> ------- ------- ------- ------- ------- ------- --------
>
> 8.58 9.54
>
>          8.26 15.61 76.13 0.00 1.19
>
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