A method is provided for operating a sliding closure for a metallurgical vessel. The sliding closure includes two tensionable fireproof closure plates opposing one another, with each of the two closure plates being slideably positioned within a corresponding housing part. Spring elements are provided for tensioning the closure plates, wherein one of the closure plates, along with its corresponding housing part, is slideable and can be moved into a closed or open position by a drive member. The method comprises: performing an offline and / or an online diagnosis of an operating condition within an area of the closure plates, by measuring at least one of size, temperature, pressure and force associated with the sliding closure so as to obtain at least one measured value, and evaluating the at least one measured value either directly or together with additional relevant process parameters; and based upon the diagnosis, either continuing use of the sliding closure or discontinuing use of the sliding closure.