Re: Yet, another Extent question ?
Date: 1995/08/22
Message-ID: <41dmhq$5gk_at_nntp.interaccess.com>#1/1
Stan Novinsky <stan_novinsky_at_jhuapl.edu> writes:
>From reading Oracle manuals and associated postings, I have a
>question about extents that may sound crazy, but..
> If the manuals say to allocate the minimum amount of Extents
> possible for objects for the purpose of better response time
> and contiguous allocatin, why is there a MIN and MAXEXTENTS ???
The manual is correct in that fewer extents (ideally just one extent) provides better response time. However, during loading or production phases of an application, sometimes the extent size is not sufficient. With proper calculations and foresight, you are correct in that you would not need to worry about MIN and MAXEXTENTS. In reality though, people can't always predict the growth of a system.
MAXEXTENTS will help you to prevent the situation where you cannot allocate another extent (limited by the OS and DB_BLOCK_SIZE), so you set MAXEXTENTS to less than the maximum allowed by the OS.
MINEXTENTS could be helpful if you need to create a large table than cannot be created in one extent (for example, UNIX has a 2GB limit on file size), so you can create several large extents in several datafiles to overcome the 2GB obstacle. This is not so good for performance, but it is the only way to overcome the OS limits.
-Ari Kaplan
akaplan_at_interaccess.com
(rest of the post follows)
> If I have a tablespace that is is defined as USER.DBF residing
> on DISKA: and is 23M why can't the INITIAL and NEXT storage
> qualifiers be used to allocate the maximum amount of space and
> don't worry about MINEXTENTS and MAXEXTENTS
> CREATE TABLESPACE user
> DATAFILE 'DISKA:[FILES]USER.DBF' SIZE 22M reuse
> DEFAULT STORAGE (
> INITIAL 11M
> NEXT 11M
> MINEXTENTS 1
> MAXEXTENTS 1
> PCTINCREASE 0);
>Thanks
>stan_novinsky_at_jhuapl.edu
>*********************************************************************
>* System Configuration: *
>* *
>* VAXstation 4000/90 * *
>* *
>* OpenVMS 6.1 *
>* Oracle 7.1, Forms 4,0 *
>* 3 RZ28's *
>* 128 Meg Mem *
>*********************************************************************
Received on Tue Aug 22 1995 - 00:00:00 CEST