Out of memory error using XML,XSLT(XALAN)

We are developing a web-application where all the pages in the site are rendered by XSL.<br> ie
When a particular page is requested, data required for that page is formed into a XML tree from the database as DOM document and the XSL file for that page is stored in the DB as text which is also retrieved and from as XSLT sourec and a jsp page will apply the XSLT transformation on the XML... through JAXP-XALAN.<br>
Every page visit increases the memory size (in the weblogic
console) and does not free up.<br>

Now what could be problem,<br>
1. We are using lots of xsl:variables in the XSL file.. is it because of this.. <br>
2. When does a xsl:variable go out of scope or released from memory<br>
3.Is there any way with which we could remove the reslutant XML tree from the memory got out of XSLT on XML<br>
4. Any other way of removing result XML tree..<br>
5. Any methods in XALAN for this..
<br>
Enviromnent:
Windows 2000 server
Weblogic 6.1
XALAN,XERCES
JAXP, DOM


<br><br>
Kindly help..