how does oracle do it, if it does that without buying advanced
compression?
Thanks
Suri

On Sep 28, 11:12*pm, RNBJ <rnbjr... (AT) gmail (DOT) com> wrote:
I am not 100% sure what you are asking but all versions of Oracle
since at least 6.0.36 have not stored any indicators or values for
trailing null columns in a row where there are no values stored in the
row trailing the null columns. So if you have a row with 10 columns
and the last five columns are nullable and no values have been
inserted for the row Oracle can skip even writing the null indicators
to the row.

Oracle has also recommended using what is now the varchar2 data type
to store character data. Varchar2 is a variable length data type that
stores only the data inserted without the need for trailing spaces.
The number data type is a form of scientific notation and is also uses
variable length storage dependent on the value stored.

So Oracle has always employed a scheme to compress the row data into
only the space necessary without actually compressing the data itself.

I hope this was what you were asking. The Concepts manual has a lot
of information in it about data types, blocks, extents, and segments
and provides a fair amount of information on how Oracle basically
works.

HTH -- Mark D Powell --