What you declare in the XML goes to the database. If you remove the XML it won't remove it from XML.
If you want to delete a unique object you can use the management portlet.
If you want to start from scratch just delete the directory you mentionned.
i have already used "<if-exists>overwrite</if-exists>" at *-object.xml.
But it still cache. i am using jboss 405GA with portal 2.4.2.
can i scratch it by config the portal-hsqldb-ds.xml ??
What do you see as "cached" ?
If you want to delete everything each time you restart the server you can modify the hibernate config files, but i doubt that's what you want to do.
If a page has been added by config file, it will always be there unless you delete it using the management portlet. Is it what you are facing ?