Here are some guidelines you should read en practice BEFORE starting on the journey called: Upgrading.
- NEVER perform an upgrade on a live store. Use a backup or dev-site!
- NEVER perform an upgrade WITHOUT a complete backup (Files and Database).
- NEVER perform and upgrade if your additional modules and Theme are not upgradable.
- DO NOT USE the upgrade script coming with 2.2.x.
- If you are an upgrading "newbie" or not familiar with OpenCart and building your own site; hire someone.
- Backup your files (FTP)
- Backup your database (phpMyAdmin, contact your hoster)
- Make a list of all your 3rd party modules and modification and find updated versions, they will NOT work after the upgrade.
- Custom theme? Contact the creator for an update as it will not work after the upgrade.
- If there are NO upgrades available for your third party modules, add-ons and theme then de-install them before upgrading.
- Use proven upgrade-scrips found in the Extensions
- Hire someone.
- If doing yourself ALWAYS use a backup/dev-site.