Re: Tablescan or TableSPACEscan

From: Sybrand Bakker <postbus_at_sybrandb.demon.nl>
Date: 10 Sep 2001 04:15:01 -0700
Message-ID: <a20d28ee.0109100315.737a4fa@posting.google.com>

"Michiel Brunt" <mbrunt_at_inergy.nl> wrote in message news:<9nhoam$qdu$1_at_scavenger.euro.net>...
> I have a tablespace that contains two tables: a very large one and a small
> one.
>
> If a query on the small table results in a full tablescan, does this mean
> that only the table data is scanned, or does the database have to scan
> through all bits that are stored in de tablespace that holds the table?
> How should the database know where the records of the small table are
> physically stored?
>
> Thanks
> Michiel Brunt

The physical representation of a table (or index or cluster) is called a segment. A segment consists of extents. The datadictionary administers segments and extents. It also administers the physical location of extents.
A full table scan will also never run across the High Water Mark of a table, so never exceeds the tables and segments boundary. These principles are described in the Oracle concepts manual.

Regards,

Sybrand Bakker, Senior Oracle DBA Received on Mon Sep 10 2001 - 06:15:01 CDT