Re: Clusters.....why?

Hi Arthur,

Arthur Merar wrote in message <35E0CFC6.28A7E2EE_at_unsu.com>...
>
>Hello,
>
>Being new to Oracle, there are a few things I do not understand. I was
>hoping someone could help me with these three things since they do not
>make any sense to me:
>
>1) What does the 'Optimal' parameter do for rollback segments?

    OPTIMAL permits you to specify an optimal length for a rollback segment. If your rollback segment extends past the optimal value you specify it automatically shrinks to the optimal size. I suggest that you get a copy of Kevin Loney's Oracle Press book, "Oracle DBA Handbook" published by Osborne McGraw-Hill.

>2) What is a cluster? Although I have read the Oracle book on
>clusters, I cannot even begin to build a picture of this in my
>mind.......

    Okay, I happen to have an application where there are three tables for each transaction. Each table has one and only one row per transaction. The table structure reflects the reporting requirements for the application where significant processing is required for each of the three tables, but there is also a considerable amount of processing where all three tables are updated and/or accessed at the same time in order to process an individual transaction. By putting the three tables in a cluster I can access all of the rows relevant to a transaction more quickly (since Oracle intermixes the tables in a cluster based on the cluster key) without significant degradation to performance when accessing only one of the three tables.

>3) When dealing with 'Profiles'....what is meant by a 'composite
>limit'?

    In essence, you have the option of establishing resource limits through the use of the CREATE PROFILE command. You can specify values for each of the resources on an individual basis. The COMPOSITE LIMIT effectively set a total that is less than the sum of maximum values for the individual resources. This gives you the flexibility to specify high limits without worrying about any one user hogging the system to the detriment of the other users.

Regards

Jerry

>
>Thank you for your help.
>
>--
>
>"A real friend is someone who knows all about you and still respects
>you."
>
>Arthur
>amerar_at_unsu.com
>ICQ#:663601
>http://www.unsu.com
>
>
Received on Mon Aug 24 1998 - 09:08:26 CDT