This function is EXPERIMENTAL. The behaviour of this function, the name of this
function, and anything else documented about this function may change in a future release of PHP
without notice. Be warned and use this function at your own risk.
dbplus_ropen() will open the relation file locally for quick access
without any client/server overhead. Access is read only and only dbplus_current() and dbplus_next() may be applied to the returned
relation.
