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"Peter" <peter_at_nomorenewsspammin.ca> wrote in message
news:cff6cvkedqaugm85sugg6mag2v47dv08rv_at_4ax.com...
> A tablespace can span more than one datafiles, but can a segment span
> more than one datafiles? I am just wondering what is the smallest
> Oracle unit that can span different datafiles.
> How about data block spanning datafiles? How about an extent?
>
We need to separate the physical from the logical here, I think.
A tablespace is a logical entity which consists of one or more datafiles. A datafile is just a file in the file system (raw devices excluded here). A segment is also a logical entity (for example a table or an index) which physically consists of one or more extents. The various extents may exist in different datafiles, but each extent will reside in a single datafile.
An extent is a collection of contiguous blocks in a datafile. The block is the lowest physical unit as far as Oracle is concerned.
Does this help?
Regards,
Paul
Received on Thu May 15 2003 - 17:00:45 CDT