Upgrading is moving to a more recent version of SMF by getting a fresh set of all the necessary files. It is used when moving from an earlier major version of SMF to a more recent one (SMF 1.1.x to SMF 2.0.x, for example). It also may be necessary to upgrade if patching does not work because of customizations or modifications to the code. If you want a clean start with the same version you have now, take a look at How to upload a fresh set of files. For more information, see upgrading