Re: help sizing extents

Hi Deb,

    Okay, there are several approaches you can take. Obviously any other than the one I recommend is either insane or inane.

    Based on their expected size I organize my tables and indexes into four groups; small, medium, large, and huge. Under this scheme I start off with the assumption that a small is an object which will not be larger than the amount of data Oracle reads from disk in one access (block size * number of blocks read), medium is up to ten times larger than small, large is up to ten times larger than medium, and huge is anything bigger. If more than 10% of your tables and indexes fall into the huge category just increase the size of the medium and large categories.

    Start off with eight tablespaces, one set of small, medium, large, and huge for tables and another set for indexes. You should add tablespaces as necessary in order to have your tablespaces all be about the same size. If you anticipate substantial growth you should increase the number of tablespaces since it is easier to move an entire tablespace to a different disk drive than it is to move selected tables from an existing tablespace into a new tablespace.

    When you create your tablespaces use a STORAGE clause and define the default INITIAL and NEXT extent at the same size and specify a PCTINCREASE of 0. I like to set the extent size at 1/4 of the anticipated size of the table.

    When you create your tables DO NOT specify a storage clause, use the tablespace defaults.

    The major advantages of this approach are that it simplifies database space management. For example it will result in every extent in a tablespace being the same size -- which guarantees that you will never have tablespace fragmentation that results in unusable fragments and you will never see misleading free space reports. Another benefit is that by using four extents per object it is relatively easy to determine your future space requirements simply by monitoring the increase in the number of extents per object.

regards
Jerry Gitomer

Deborah Felmey wrote in message
<7psfa5$oia$1_at_autumn.news.rcn.net>...
>I'm an oracle newbie. We are moving our current databases to a
new
>platform - we are placing the current datafiles into one
datafile when we
>do the conversion - my question is - is there a formula for
figuring out
>what the initial extent and next extent will be? How large is
too large?
>
>Also - we are running version 7.3.4 - what is the best way to
run exports on
>existing data - for import into the new database?
>
>Any help is greatly appreciated.
>lost in pasadena - deb
>
>
Received on Tue Aug 24 1999 - 08:37:26 CDT