Detailed upgrade instructions that help you retain your customizations while upgrading to new features, can be found in your ZIP file under the /docs/2.Readme-Upgrade.html file and also in this related FAQ article
A. ALERT: If you want to preserve your CUSTOMIZATIONS, use these instructions INSTEAD: upgrading and preserving customizations
B. If you have NO CUSTOMIZATIONS to preserve, here's a high-level overview/summary of a slightly shorter process:
- Back up your site from the server as well as the copy on your computer.
- Backup your database
- Create a new directory and copy your site into it
- Then create a new database and load your old database in it
- Next, change the two configure.php files to utilize the new directory and database
This way ... when you attempt to upgrade you are "practicing" to see where the problems, if any will happen
- Make sure all appears to be working on your temp site.
- Now load the "new" version files to your new temp directory (from latest downloaded ZIP)
- Run the http://www.your_domain_name.com/your_new_site/zc_install
- Choose the Upgrade Database option
- Process each suggested step one at a time ... leave the first checkbox that the upgrader picked checked and uncheck the others.
-Advantage is that you can see your problems step by step
-Each time it completes it will recheck the boxes left to go.
-Continue in this method until all boxes are unchecked.
- If you find you have issues, you are not hurting anything and can always start over without damage to your existing shop and live database.
Reminder: Read the /docs/2.readme-upgrade.html document for step-by-step details and information on tools to help in the process.
QUESTION: "Why is this process so long?"ANSWER: Another way to look at it is this: An "upgrade" is essentially a rebuilding of your site.
The steps outlined above are the recommended way to do it so that you rebuild your site in a temporary location, letting you resolve all potential problems *before* you ever touch your actual live site. This gives you time to sort out whatever needs sorting "just in case", and allows you to keep taking sales while you're preparing the upgrade. It also helps take some of the pressure off and makes it less urgent to do it all in one fell swoop.
The process of comparing your site against the original code for the old version is, in one sense, to simply help you quickly identify what customizations you need to make to put those same capabilities into your new site. It simply speeds the process and creates a sort of checklist of things for you to re-do on your new site.
Then, after you've got it all built in the temporary location, you put your live store down for maintenance, quickly redo the upgrade there, and then bring it online ... meaning your actual live store's downtime could be as short as 5-10 minutes depending on complexities etc.
So, follow the guide, and while there may be some learning involved and remembering of things you did awhile back, it's all time well spent.