ok, so should the number of extents in a table be considered in table design? there
are alot of .pdfs and people on this listserv that say it is irrelevant?
>
> From: Rachel Carmichael <[EMAIL PROTECTED]>
> Date: 2003/06/20 Fri PM 02:44:52 EDT
> To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
> Subject: Re: oracle docs do say # of extents effect performance
>
> or reasonable to WANT? if I'm running a data warehouse, maybe. If an
> OLTP system, orders and customers etc then I'm not likely to WANT the
> next block of data on disk for my transaction
>
>
> --- Darrell Landrum <[EMAIL PROTECTED]> wrote:
> > My favorite part is
> > "and all of the table's data will be stored in a relatively
> > contiguous
> > section of disk space".
> >
> > Is this even reasonable to believe, especially with any kind of
> > striping implemented?
> >
> > >>> [EMAIL PROTECTED] 06/20/03 12:00PM >>>
> > Two reasons:
> >
> > a) if you go into extent map blocks then you will
> > suffer an overhead of at least 1 billionth of a
> > percent :-)
> >
> > b) more seriously, its generally easier to pick up a
> > "rogue" table if its run into thousands of extents and
> > you had not intended it to. Its not a performance
> > problem per se, but its indicative that its a segment
> > thats doing something that was unforseen in the design
> > phase..
> >
> > hth
> > connor
> >
> > --- [EMAIL PROTECTED] wrote: > I just read a .pdf by a
> > couple of people at oracle
> > > called Stop Fragmenting and start living where it
> > > says not worry about the number of extents in a
> > > tablespace. However in the administrators doc it
> > > says the following:
> > >
> > > Estimate Table Size and Set Storage Parameters
> > > Estimating the sizes of tables before creating them
> > > is useful for the following reasons:
> > >
> > > You can use the combined estimated size of tables,
> > > along with estimates for indexes, rollback segments,
> > > and redo log files, to determine the amount of disk
> > > space that is required to hold an intended database.
> > > From these estimates, you can make correct hardware
> > > purchases and other decisions.
> > >
> > > You can use the estimated size of an individual
> > > table to better manage the disk space that the table
> > > will use. When a table is created, you can set
> > > appropriate storage parameters and improve I/O
> > > performance of applications that use the table. For
> > > example, assume that you estimate the maximum size
> > > of a table before creating it. If you then set the
> > > storage parameters when you create the table, fewer
> > > extents will be allocated for the table's data
> > > segment, and all of the table's data will be stored
> > > in a relatively contiguous section of disk space.
> > > This decreases the time necessary for disk I/O
> > > operations involving this table.
> > >
> > > this is at the following link:
> > >
> > >
> >
> http://download-west.oracle.com/docs/cd/A87860_01/doc/server.817/a76956/tables.htm#208
> >
> > >
> > > am I reading this wrong or is Oracle stating that
> > > you should have less extents in a table? I know
> > > several people on here have posted that the number
> > > of extents used by an object is almost irrelevant.
> > >
> > > --
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> Author: Rachel Carmichael
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Received on Fri Jun 20 2003 - 13:37:34 CDT
