Yes, This question is more suited for the Oracle Spatial Forum.
And about the question, you must use Esri's owns products like ArcCatalog or Arcmap to connect to oracle and change the format of your geometries. Arcgis is capable of storing geometrical data in oracle in SDO_Geometry format.
If you have question about the procedure of this action, don't hesitate to ask.
ArcGIS (ArcSDE) supports sdo_geometry. So the simplest is to do what Farid suggested. Use ArcGIS/ArcCatalog to convert, store, and use sdo_geometry (with no change to the apps) as the storage format.
If you'll want to convert and keep a copy you can use a spatial ETL tool like FME (from Safe Software).