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

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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