split big DOM xml file ??

How can i split big DOM xml file in to small files?

You could do that in two ways:

1) Use XML entity references in a top-level XML document to "include" other XML documents. This approach splits the file, but the DOM parser will still read it as one big XML document.

2) Split the XML document and write Java code to merge the documents together after parsing each.

Could you explain a bit more about why you need to split the big file?

If i use big DOM xml file, it occupies more memory. I want to reduce this..

If it is about parsing a big xml file and working with the nodes, u can use SAX parser. SAX is event based. Hence, memory constraints are reduced.

I think the important question is - what kind of processing do you have to do with the big XML file?
For a simple pass through the entire document, extracting specific information, SAX processing will use very little memory.
If you have to modify the document structure extensively and rewrite it you may be buying more memory...

How big are we talking about anyway?
Bill