Re: Re: what's mean of "enqueue hash chains" latch?

From: eygle <oracle.unix_at_gmail.com>
Date: Sun, 9 Jan 2005 13:24:40 +0800
Message-ID: <1cf1ebe90501082124476e2b30@mail.gmail.com>

hi,biti_rainy;

I don't think parallel process's locks are all put on the same list. If so,Does it mean all parallel will fall into contention destined?

And we have _enqueue_hash_chain_latches =6 ,default to cpu_count. With parallel 4 and _enqueue_hash_chain_latches =6, and why so much contention?

Maybe the explain is just like you said :the parallel process's locks are all put on the same list.

On Sun, 9 Jan 2005 12:14:42 +0800, biti_rainy <biti_rainy_at_itpub.net> wrote:
> hi,eygle
>
> i think the 'enqueue hash chains' looks like the 'cache buffer chains',oracle often use * hash table + list * to manage resource. enqueue resources would be put on the list blow some hash bucket.
> so ,i am not sure whether the parallel process's locks are all put on the same list. if they always on the same list ,you would not use parallel insert. if not,you would increase the _enqueue_hash to a prime number.
>
> there is my 9i database:
> sys_at_OCN>select INDX from x$ksppi where KSPPINM = '_enqueue_hash';
>
> INDX
> ----------
> 82
>
> sys_at_OCN>select KSPPSTVL from X$KSPPSV where indx = 82;
>
> KSPPSTVL
> ----------------------------------------------------------------------------------------------------
> 177
>
> sys_at_OCN>show parameter dml_locks
>
> NAME TYPE VALUE
> ------------------------------------ ----------- ------------------------------
> dml_locks integer 312
> sys_at_OCN>show parameters enqueue_resource
>
> NAME TYPE VALUE
> ------------------------------------ ----------- ------------------------------
> enqueue_resources integer 532
> sys_at_OCN>
>
>
> Best regards
>
> msn: biti_rainy_at_hotmail.com
> a dba from alibaba(china)
>

---

eygle,a beginer of Oracle from China.
my site: http://www.eygle.com

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Received on Sat Jan 08 2005 - 23:24:36 CST