JMS v. 1.2.43
JomSocial 2.2.2 (upgrading from 1.8.7)

When I originally set up multisites, I removed some of the connections between the databases in JomSocial between the master and slave sites. For example, the activity stream is not connected, so each site can have its own unique stream.

However, I do not know how to upgrade JomSocial among my sites now. Simply upgrading on the master site left database errors on my slave site, so I uninstalled JomSocial directly on my slave site, and then re-installed it through Multisites. Now, unfortunately, the database overwrote the slave site database, which means I lost the data from the slave and have to un-link them again.

Obviously, I screwed up! Can you tell me the proper way to handle this so I don't screw up again?

Thanks!

In the user manual chapter 8 we describe the difference between update and upgrade.
Update mean only PHP code update and no DB layout modification. This is for example security fixes or bug fixes.

Upgrade mean that the DB layout is modified.
When upgrading an extension in the master that also has an impact in the DB layout, you have to re-apply the install in each slave site to let the extension proceed with the DB layout modifications.

In case of JomSocial, this was more complex because this extension has 2 names.
A public name = 'JomSocial' and an internal name that is 'Community'.
So the problem is to re-install JomSocial from a slave site.

In JMS 1.2.58, we changed the Slave site installer to now accept 'Community' as a synonym of 'JomSocial'.
So now you can re-install JomSocial from a slave site to let it perform the DB modifications.
The procedure to get the latest version is present in the FAQ.
www.jms2win.com/en/faq/faq-joomla-multi-sites#cat-122