Upgrading from lower version to an upper version must be done step by step, first please, please, please take a back up of all your files from both ojs and database as well. Similarly Export all your articles and journals and then go for upgrade.
Take a look over these links (database upgrading is also given in it)
@abraham.john, since the question references 2.4.7 as the upgrade target, be sure to switch the git “branch” to “ojs-stable-2_4_7” when adding the GitHub link. This will grab the 2.4.7 UPGRADE doc instead of the the master (3.x) UPGRADE doc.