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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Initrans (don't forget deadlock avoidance)
I've generally found that most "block level contention" e.g. buffer busy waits,
data block waits, segment header waits etc. is influenced much more by
freelists and freelist groups than it is by initrans.
A good paper on the subject is:
Freelist Management with Oracle 8i by Stephan Haisley
Also Tom Kyte's Expert One on One Chapter 6 Database Tables (Freelists)
Sorry but I only have a hardcopy of Stephan's paper and no URL
Cheers,
Chris
Quoting "Mark W. Farnham" <mwf_at_rsiz.com>:
>
> So in addition to avoiding ITL waits, I would also say to pre-emptively set
> INITRANS when you need to systematically guarantee no deadlocks.
>
> Of course this also implies that the architecture of your system includes a
> way to control the maximum number of updating threads against a given set of
> tables. If you don't have that, I don't believe you can guarantee no
> deadlocks in multi-table transactions.
>
>
>
> If someone knows another way to guarantee no "false deadlocks" due to
> insufficient ITLs, I'll gladly be educated.
>
>
> Regards,
>
> mwf
>
> -----Original Message-----
> <snip>
>
> No, don't set INITRANS to a non-default value unless you need to do so
> to avoid ITL waits. ITL waits are counted in V$SEGSTAT. The ITL can
> grow dynamically and preallocating extra slots just wastes space.
> Instead, ensure that you never set PCTFREE to zero, except on truly
> read-only tables.
>
> Only set FREELISTS on tables that get enough concurrent inserts to
> cause dynamic ITL growth. Take a few block dumps, and use the highest
> ITL size seen, raised to the next prime. There is very little downside
> here, only a few more block below the HWM, so you don't have to be too
> careful.
>
> @ Regards,
> @ Steve Adams
> @ http://www.ixora.com.au/ - For DBAs
> @ http://www.christianity.net.au/ - For all
>
> -----Original Message-----
> <snip>
>
> I have heared the best number for Initras is the number of CPU but what
> about the Freelists is there any standard for this parameter too.
> Any idea for any standards for these two parameters? Number of CPU or
> average number of Transaction or what?
> Thanks,
>
>
> Hamid Alavi
>
> <snip>
>
>
> --
> To unsubscribe - mailto:oracle-l-request_at_freelists.org&subject=unsubscribe
> To search the archives - http://www.freelists.org/archives/oracle-l/
>
Chris Dunscombe
Christallize Ltd
-- To unsubscribe - mailto:oracle-l-request_at_freelists.org&subject=unsubscribe To search the archives - http://www.freelists.org/archives/oracle-l/Received on Fri Sep 10 2004 - 02:59:16 CDT
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