Re: Re: what's mean of "enqueue hash chains" latch?
- From: eygle <oracle.unix@xxxxxxxxx>
- To: biti_rainy <biti_rainy@xxxxxxxxx>
- Date: Sun, 9 Jan 2005 13:24:40 +0800
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@xxxxxxxxx> 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@OCN>select INDX from x$ksppi where KSPPINM = '_enqueue_hash';
>
> INDX
> ----------
> 82
>
> sys@OCN>select KSPPSTVL from X$KSPPSV where indx = 82;
>
> KSPPSTVL
> ----------------------------------------------------------------------------------------------------
> 177
>
> sys@OCN>show parameter dml_locks
>
> NAME TYPE VALUE
> ------------------------------------ -----------
> ------------------------------
> dml_locks integer 312
> sys@OCN>show parameters enqueue_resource
>
> NAME TYPE VALUE
> ------------------------------------ -----------
> ------------------------------
> enqueue_resources integer 532
> sys@OCN>
>
>
> Best regards
>
> msn: biti_rainy@xxxxxxxxxxx
> a dba from alibaba(china)
>
----------------------------------------
eygle,a beginer of Oracle from China.
my site: http://www.eygle.com
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