The only way to properly convert from an Enterprise Edition back to a Standard Edition is through an Export/Import operation. This way you will get rid of all Enterprise Edition specific Data Dictionary objects, as the SYS schema objects are not exported. After the Import in the Standard Edition database, you only need to drop all user schemas related to Enterprise Edition features, such as the MDSYS account (used with Oracle Spatial). NOTE: You CAN convert from EE to SE by running the CAT* scripts, but you may see objects in the data dictionary that no longer apply. If you do not want to cleanup the invalid objects, then you will have to install the EE software, create a database and import.