Probably not. You would end up with 5.6 code trying to run off a 5.5 database. The 5.6 upgrade process modifies some tables to bring in the new permission system and I expect other tables as well. There were similar changes to tables made by the 5.4 to 5.5 upgrade.

However, you have hit on half of my personal zero risk upgrade strategy.

I like to create a sub-domain such as new.mysite.com, clone the existing site to run under that sub-domain. Then make the upgrade to the cloned site. Test it. If all runs well, swap the main domain name to point at the folder where the sub-domain lives (and the old site can just sit unused until I am happy to delete it). if not, I can try again having never risked the live site.

This runs into complications if the live site has dynamic content, such as membership, forums or ecommerce.

In that case, having succeeded once and learned any issues with the sub-domain, I then put the main site in maintenance mode while repeating it again with the same sub-domain, or yet another sub-domain. If it works, I then swap the main domain, If it does not, I can take the original out of maintenance mode again having never risked a live site, do some investigation and repeat until successful.

The key is to never risk the live site, learn on a cloned staging site, then swap once everything is stable.

The only disadvantage is the time the main domain is in maintenance mode while doing the final clone & upgrade.

Hey John,

Good strategy and I do completely agree, sadly this platform doesn't seem to have the stability to trust automated updates, never has one succeeded across multiple sites :o(

I will give your suggestion a go and report back on any errors that I hit, I expect to unfortunately.

Cheers, Ash