Which more performance hit: trip to DB, traverse XML DOM in memory?

Question

Which is more of a performance hit:
     1. Make trip to DB, get Data, come back
          a. Includes Make trip to DB, alter smth, come back
     2. Use DOM Parser to get data from XML (XML is in Memory)
          a. Includes altering the DOM Document that is in memory

Answer 1

The trip to the DB depends on network latency and sometimes (but not often) network speed and of course the complexity of doing the update on the DB (how many indices chang, what trigggers fire, what integrity constraints must be validated, etc.).
The XML parsing is generally done once and from then on you manipulate the tree directly - that latter part is efficient. Of course the cost depends on your technique, the hit taken to parse the XML (which parser? validating?).
The first part will probably consume less CPU on the host running the Java program (assuming DB is remote) but take more time total.
The latter may (or may not) consume more local CPU but should be faster.
Your mileage may vary. Test it.
Chuck.