It doesn't seem to be as easy, as one might expect - due to the hibernate persistence layer.
I haven't a working solution now, below you'll find the steps to get at least a connection and a db-schema :-/
The main changes are related to the hibernate relation mapping. The xwiki
mapping contains "string" types with a size of > 4k. hibernate stores
these as "long" (oracle long), this is not appropriate. I've changed
"string" to "text" (where size > 4k)
(See attached files)
modify the hibernate configuration path in xwiki.cfg:
modify the hibernate.cfg.oracle.xml file (attached) to enter the right connection data.
create a directory .../xwiki/WEB-INF/classes
put the attached file xwiki-oracle.hbm.xml there.
Put the odbc-drivers (ojdbc14.jar) into ../xwiki/WEB-INF/lib
If you start xwiki now, you should get a connection, the db-schema should get created. I'm getting the following error while accessing xwiki:
ERROR P1-19 org.hibernate.util.JDBCExceptionReporter - ORA-01400: Einfügen von NULL in ("WIKI"."XWIKIDOC"."XWD_TITLE") nicht möglich
I've tried to change all the not-null columns to null (as it is easier than to change the contraint to deferrable & deferred), but it does not help.
At this point, some debugging seems to be necessary...
An article of interest might be http://jira.xwiki.org/jira/browse/XWIKI-838