oracle Jdbc update statement return zero

[plusav84]

This is regarding sql update statement using JDBC. Actually I'm looking into some issue we had, which all come to hang at a point where update statement has returned zero while trying to update certain row.Now to make it clear,THE SPECIFIC ROW UPDATE STATEMENT IS TRYING TO UPDATE DO EXIST in the table.So there is no possibility of record not found and hence zero update.Having mentioned that, my question is, do you see or is their any other possibility where zero can be returned by the update. I'm using oracle jdbc driver. so do oracle jdbc mention any scenario where zero can be returned by the update statement other than record not found.Many thanks,Ameer Mawia