Oracle migration : size on disk of data file greater in PG

Hi,

At a customer site, we've made a migration from Oracle 8.1.5 to PGSQL
8.1.1. The migration happened without any problem and now the performances
are better with PG than with Ora, but the customer noticed that the size
of PG on disk where much greater than the size on disk of Oracle. And I'm
not able to find an easy explanation.

Is it normal, due to inner data storage mecanisms differents between
Oracle and PG ?

Of course, we've run VACUUM on both DB before measuring the size on disk.

The database is used to store statistical data by month and therefore
contain dozen of tables of the same layout containing most of the time
hundred of thousands records.


Thank you,

Benoit Gerrienne