Re: Oracle internals.

> > 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 ? Received on Sun Dec 09 2001 - 14:07:11 CST