(Hitting head with flat of hand) Doh! Even done that myself.
Thanks for the reminder.
Jim
"Thomas Kyte" <tkyte_at_us.oracle.com> wrote in message
news:9v0nr00279n_at_drn.newsguy.com...
> In article <_OPQ7.20640$wL4.36406_at_rwcrnsc51>, "Jim says...
> >
<snip>
>
> not so -- CLUSTERS give you the ability to store data from many segments
> (tables) on the same database block. The oracle data dictionary is
littered
> with them (you use them all of the time).
>
> a database block may be used by MANY objects simultaneously. happens
everyday
> with the data dictionary. It is a way to store "pre-joined" data.....
>
>
>
>
>
>
> >
> >"Andrej" <andrej611_at_wp.pl> wrote in message
> >news:9v0g9g$ji8$1_at_korweta.task.gda.pl...
> >> > > I am looking for the following info concering Oracle internals:
> >> > > - how does Oracle know what blocks are assigned to what tables ?
does
> >is
> >> > > blindly scan throug all the blocks ?
> >> >
> >> > No, it holds that information in data dictionary tables.
Specifically,
> >> UET$
> >> > records what extents exist, and who owns them. Tables such as OBJ$
and
> >> TAB$
> >> > also come into play. In locally managed tablespace, a bitmap at the
> >> header
> >> > of the tablespace indicates whether a block is reserved for use or
not.
> >> > Data dictionary entries still say which object owns which block.
> >>
> >> But data dictionary is also a bunch of TABLE(s). So your asnwer
produces
> >an
> >> infinite loop ... it knows where the table blocks are by querying a
table.
> >>
> >> I am trying to find out how Oracle recognizes what tables ARE in a
SYSTEM
> >> tablespace datafiles and how are blocks internaly linked with them -
for
> >> example what blocks make UET$.
> >>
> >> > >So where is a
> >> > > glue that holds a blocks/extents of a segment toegether ?
> >> >
> >> > There is no such substance.
> >>
> >> There must be. Otherwise Oracle wouldn't work at all. A single block
holds
> >a
> >> data about rowids in the header. But how is data distionary build so
that
> >> Oracle knows where to look for rows making a single schema object ?
> >>
> >>
> >>
> >>
> >>
> >
> >
>
> --
> Thomas Kyte (tkyte@us.oracle.com) http://asktom.oracle.com/
> Expert one on one Oracle, programming techniques and solutions for Oracle.
> http://www.amazon.com/exec/obidos/ASIN/1861004826/
> Opinions are mine and do not necessarily reflect those of Oracle Corp
>
Received on Sun Dec 09 2001 - 20:30:47 CST
