Create Big XML files ( extract ) from Relational Tables

Question

Experts: I need to create a big XML extract more than 5Gb , from relations tables using SQLX. I read the excellent FAQ given by MDrake in the following thread.
https://forums.oracle.com/thread/418001
Question
1) Is it better to use XML schema, My XML output format is pretty much going to be static, so I can register an XML schema .
2) Does Registering the XMLschema help with better memory management. I recall I used to get out of memory exception when I generated xml documents on oracle 10g using DBMS_XMLGEN.
3) Can I generate this 5 Gb of XML file using oracle's default DOM parser?
Thanks
Kevin

Answer 1

Hi Kevin,
1) Is it better to use XML schema, My XML output format is pretty much going to be static, so I can register an XML schema .
2) Does Registering the XMLschema help with better memory management. I recall I used to get out of memory exception when I generated xml documents on oracle 10g using DBMS_XMLGEN.
No, an XML schema won't help for the generation.
It is useful though if you're looking for the opposite task, i.e. loading an XML file into database tables.
3) Can I generate this 5 Gb of XML file using oracle's default DOM parser?
What is the default DOM parser ? Do you mean DBMS_XMLDOM APIs?
Since you want to generate XML, there's not much to parse.
Generally, using SQL/XML functions is the way to go.
You may still hit some performance/memory issues while reaching such a size, especially with large XMLAgg aggregation context.
If you do, you may switch to chunk generation instead. I've got some pretty good result with this approach and the parallel query feature.