Ah, I see you have found it :-) (the C bit contra Java wrapper bit) From: Jeremy Schneider <jeremy.schneider@xxxxxxxxxxxxxx<mailto:jeremy.schneider@xxxxxxxxxxxxxx>> Date: Wed, 3 Aug 2011 02:43:36 +0200 To: Marco Gralike <marco.gralike@xxxxxxx<mailto:marco.gralike@xxxxxxx>> Cc: Oracle-L <oracle-l@xxxxxxxxxxxxx<mailto:oracle-l@xxxxxxxxxxxxx>> Subject: Re: faster way to create XML export We just finished a test run with DBMS_XMLGEN on the same dataset -- it finished in 2 sec. Still used dbms_xslprocessor.clob2file for filewriting. Looks like this will do most everything I mentioned - just working on the last step now, getting the XSLT headers. (Seems to be a function for this but it's not well documented and didn't seem to work on our first try...) Also, I noticed something in the oracle docs here: http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14252/adx_j_xsu.htm#sthref546 "Note: For increased performance, consider using DBMS_XMLGen and DBMS_XMLStore as alternatives to DBMS_XMLQuery and DBMS_XMLSave. The former packages are written in C and are built in to the database kernel. You can also use SQL/XML functions such as XML_Element for XML access in the database." No kidding - way faster! Wish I'd seen this before! :) -Jeremy On Tue, Aug 2, 2011 at 6:34 PM, Jeremy Schneider <jeremy.schneider@xxxxxxxxxxxxxx<mailto:jeremy.schneider@xxxxxxxxxxxxxx>> wrote: Oh yeah, we also tested with the DBMS_XMLQuery package - it seemed to take about as long as the Oracle Serializer java code. On Tue, Aug 2, 2011 at 6:19 PM, Jeremy Schneider <jeremy.schneider@xxxxxxxxxxxxxx<mailto:jeremy.schneider@xxxxxxxxxxxxxx>> wrote: Well we're not making any 1GB files yet, but I can't really imagine what anyone does with a 400MB file either. Anyway - we were doing some testing with a much smaller "test" dataset (8MB file), and we tried Marco's idea. Here are the results: Original Code: 96 sec Oracle Serializer: 40 sec Marco's Code: 3 sec :) Sweet! However, it seems that there's an implicit conversion from XMLType to CLOB and it's not immediately obvious how to control the XML that's generated. I guess it's time for me to learn some more about XMLDB. :-/ Here's what we're trying to figure out how to do with XMLType: - xmlQuery.keepCursorState(true); - xmlQuery.setMaxRows(pRowLimit_variable); // Note: we continue with cursor and split output to multiple files - xmlQuery.setRowTag(pRowHeader_variable); - xmlQuery.setRowsetTag(pRowHeader_variable+"_MYSUFFIX"); - xmlQuery.setDateFormat("yyyy-MM-dd'T'HH:mm:ss"); - xmlQuery.setStylesheetHeader(pXSLtURI_variable); Any tips would be appreciated... -J PS - this blog post by Marco is excellent: http://www.liberidu.com/blog/?p=369 On Tue, Aug 2, 2011 at 4:41 PM, Marco Gralike <Marco.Gralike@xxxxxxx<mailto:Marco.Gralike@xxxxxxx>> wrote: ONE 1++GB in XML document, are you serious. Wouldn't be surprised though. I see it more and more often. ;-) No the stuff showed below is in C and/or even part of the C kernel. It is possible to do in SQL and yes due to the fact that it is 1 XML document you will get in trouble regarding those mentioned sizes per XML document. I am guessing, although never really checked that if you switched it again for a C based SAV serializer it would be even faster or does it reside in the JVM database kernel? I wonder which part picks up those big XML documents and tries to do something useful with it. Work to be done with those documents afterwards most be very resource intensive ;-) -- http://www.ardentperf.com<http://www.ardentperf.com/> +1 312-725-9249<tel:%2B1%20312-725-9249> Jeremy Schneider Chicago -- http://www.ardentperf.com +1 312-725-9249 Jeremy Schneider Chicago