Let's say I had a shop in the directory:
/catalog
and a database called: something_v136
I would make a new directory:
/new_shop
and a database called: something_v138
Then I would copy my files from /catalog to /new_shop and I would load a copy of my database something_v136 into the database something_v138 ...
Next, you need to edit the two configure.php files:
/includes/configure.php
/admin/includes/configure.php
and change the paths for /catalog to /new_shop and the database information from something_v136 to something_v138 and the username and password as needed ...
I would then make sure this works ... if possible, on the new server ...
If not, I would then load all the files from Zen Cart v1.3.8a to /new_shop and run the Upgrade on the database ... remember the NEW database is: something_v138 and this is the database to be upgrading ...
Then I would use something like Beyond Compare from scootersoftware.com to see what changes are needed on my templates and override files ...
Next I would test everything in the new version to make sure it works from create an account to shopping to checkout ... and the Admin etc.
Once all is well and working perfectly ...
I would set my Live site Down for Maintenance ...
Backup my Live database again and drop all tables from my new database something_v138 and reload the backup from something_v136 and Upgrade the database something_v138 again ...
This is to give you a current version of your shop and not miss any new orders, customers etc. while you were working on getting the new upgrade working ...
Once all is done ... I would test everything on the /new_shop again ...
NOTE: you are set for Down for Maintenance on the /new_shop and should turn that off for testing as many shipping and payment modules cannot function right with that on ...
When all is well ...
Set the NEW site Down for Maintenance ...
Change the 2 configure.php files to reflect the old path /catalog vs /new_shop but leave the new database something_v138 alone as that is your NEW Live database for this version ...
Rename the directory /catalog to /old_shop and then rename /new_shop to /catalog ...
Test test test ...
If all is well ... you can now turn off the Down for Maintenance and you are back up and online with your shop ...
Easy Smeazy, eh? :smile: