svn merge

How reliable is svn merge? What changes are that it fails with success(instead of throwing a conflict it does a wrong merge)?

svn merge

Hi, I have 30 files that I want to merge, but I do not know which would be the easiest and much efficient and save way to do so. I have the main production line Z and two other branches X and Y. All of the branches are still in production since X and Y are minor releases. Therefor on a time