You are right.
If Oracle will scan all extents of the table it finds the information as to
the physical location of these from the data dictionary. It does not scan
the tablespace.
If on the other hand it uses an index access path then the rowid gives the
physcal location of the row on disk.
--
Niall Litchfield
Oracle DBA
Audit Commission UK
"Thomas Schwickert" <schwickert_at_yahoo.com> wrote in message
news:f82e5d3f43e745eb9166a1b3bd56bc8e.20305_at_mygate.mailgate.org...
> Hi,
>
> "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
>
> as I suppose (someone should correct me if I'm wrong), Oracle do really a
> TABLE -SCAN, not a TABLEspace-SCAN (opposite to DB2, at least in Version
> 4 on MVS).
> Oracle internally stores data about tables where to find them.
> In dba_extents / dba_segments you see FILE_ID / BLOCK_ID
> or HEADER_FILE / HEADER_BLOCK.
> With this informations, oracle knows where to look.
>
> Hope that I say some right :-)
>
> Thomas
>
>
> --
> Posted from [212.20.131.226]
> via Mailgate.ORG Server - http://www.Mailgate.ORG
Received on Mon Sep 10 2001 - 03:51:09 CDT
