I have a production site like www.example.com and I use 2 subdomains test.example.com and stage.example com for testing and staging purposes. Each of these 3 versions of the site uses it's own database. The user and password is the same for all 3 databases, but of course the database names differs. I have checked and double checked that the correct database names are set in the settings.php file for the 3 sites, respectively.
Nevertheless, when I do a content change in one of these 3 site versions, that same change becomes immediately visible in all 3 sites.
I have tried to turn off all my caching modules, like Boost and Memcache and Content.
EDITED: I have now narrowed it down to a caching problem. If I flush all cache in the site that shows the wrong content, it reverts to the right content. So content changes ends up in the right database. But as I said, even though I have all caching turned off, and all caching modules are disabled, all content changes in one site are immediately reflected in the 2 other sites (until I flush all cache in these 2 other sites).
Does anyone have an idea about where to look? Some common caching in the server environment?