Have you ever had to make fundamental changes to a table in Oracle, but haven't been able to get any downtime? I'm talking things like:
* Dropping columns
* Shrinking allocated space
* Removing chained blocks and restoring the PCTFREE
This video shows how to copy a database user from one database to another user DBMS_METADATA. It also shows how to copy a user's permissions and discusses password hash differences between Oracle 10g and 11g.