Re: Mechanism of building index with parallel

Hello David,

  Here you go:
" Parallel index creation works in much the same way as a table scan with an

     ORDER BY clause.
     The table is randomly sampled and a set of index keys is found that
equally
     divides the index into the same number of pieces as the
     DOP(Degree of Parallelism).
     A first set of query processes scans the table, extracts key, ROWID
pairs,
     and sends each pair to a process in a second set of query processes
based
     on key. Each process in the second set sorts the keys and builds an
index
     in the usual fashion. After all index pieces are built, the parallel
query
     coordinator simply concatenates the pieces (which are ordered) to form
     the final index.

Regards,

  Ron
  DBA Infopower
  http://www.dbainfopower.com
  Standard disclaimer:
http://www.dbainfopower.com/dbaip_advice_disclaimer.html

"David" <david_at_david.nospam.com> wrote in message news:c1i52i$ij31_at_imsp212.netvigator.com...

> Hi all,
>
> COuld anyone provide me the information of how to handle the parallel
> option in building index in Oracle? For example, if I build an index with
> parallel 5, then 5 threads will do the job. Is 5 segments created (each
> doing a small part of data, and each is reading, sorting and writing), and
> then merge together? Or 5 threads each doing different part of job, such
as
> one is reading the data, one is writing the data, one is sorting etc. I
have
> the experience that when building index with parallel option, the file
size
> need to build is larger (index tablespace, not temporary tablespace). When
I
> build the index with noparallel, the index is created successfully without
> adding extra file on the index tablespace. Could anyone explain the reason
> behind this?
>
> Thanks,
> David
>
>
Received on Sat Feb 28 2004 - 01:00:30 CST