Re: Oracle8 ROWIDs - data file numbers

In article <89j8i0$l0t$1_at_nnrp1.deja.com>,   Thomas J. Kyte <tkyte_at_us.oracle.com> wrote:
> In article <89hnid$k2d$1_at_nnrp1.deja.com>,
> Ben Ryan <benryan_at_my-deja.com> wrote:
> > The New Oracle8 ROWID format
> >
> > The Oracle8.0 "new features" courses talk about the file number
> > component of the ROWID as being the relative data file number
> > within the tablespace. (In Oracle7 the datafile component of
> > ROWID is the absolute data file number within the database.)
> >
> > I cannot produce an example that shows the difference. My attempt
> > below shows a partitioned table with two partitions containing two
> > rows, one in each partition, with each partition being in a
> > different tablespace.
> >
> > When I compare the relative data file numbers with the absolute
> > data file numbers I do not see any difference. I would have
> > expected the relative file number to be, say, 1 (meaning first
> > data file within tablespace).
> >
> > Can anyone give me an example which would show the difference.
> >
>
> you would have to create a database with lots (thousands) of files.
> The relative file number will be a 2 byte integer. The absolute file
> name is a 4 byte integer in 8. The relative will equal the absolute
> until you get a whole mess of files in there. The relative file
> number is by tablespace and was kept a short integer to avoid have
> to change the internal format of a rowid.
>
> --
> Thomas Kyte tkyte_at_us.oracle.com
> Oracle Service Industries Reston, VA USA
> --
> Opinions are mine and do not necessarily reflect those of Oracle Corp

Thanks for the response,
I looked in the Oracle8.0 Server reference - Chapter 5: Database Limits - Table 5-2 Physical database limits - And it claims that the maximum number of database files per database is 65533 (i.e. less than 2 bytes). I also checked for 8.1.5 where it is also 65533.

Now, I am guessing, that you are looking at one of the base tables of the system dictionary and hence you can see it is stored in a 4 byte structure.

So is this relative-to-tablespace data file number, something that is not used currently, but will be used? Or am I being slow on the uptake?

Thanks, Ben

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Before you buy. Received on Wed Mar 01 2000 - 00:00:00 CST