Re: DBA - clustered tables - WHY ? - WHO USES THIS ?

roosens wrote:
>
> In the seven year I work with ORACLE , and this in several major (Belgian) companies,
> I never came across anyone using CLUSTERED TABLES.
>
> Could any point out the advantage- when you should use or more important when NOT to
> use them.
> How can you estimate the profit ?
> How can you measure your profit after applying them ?
>
> Who will let us join his experience ??
>
> Thanks.
>
> ir Danny Roosens
> Genesys - Belgium

I've not used them yet. The Oracle 7 Server Administrator's Guide (Dec'92)
has a lengthy discussion on pages 8-41 through 8-60.

Some of the recommendations that they make are:

1.) Use clusters to store one or more tables that are primarily queried

    (not predominately inserted into or updated) and for which the queries

    often join data of multiple tables in the cluster or retrieve related

    data from a single table. page 8-41 and 42.

    This technique probably, as another has already observed, gives you a speed

    advantage in that the leaf containing the desired rows may already be

    memory resident allowing you to take advantage of the disk cache.

2.) Select cluster keys carefully. This warning is because if you pick

    unpopular keys, the chances of the desired row being in memory is not

    is low and causes more disk accesses which will kill performance.

3.) Clusters will take more space. 8-42

    I hope that this helps

-allan hicks Received on Thu Aug 08 1996 - 00:00:00 CEST