Please use the following instructions when upgrading activeCollab to the latest release, to keep system downtime to a minimum:
/activecollab and /public/assets are the largest folders and can take a while to upload. That is why we recommended uploading them separately, and later renaming them, instead of overwriting the existing files.
When you've finished the upgrade process, be sure to check everything is working as expected. Once you've verified that everything is up and running, you can delete the old versions of the/activecollab and /public/assets folders, , or keep them for backup, just in case.
This approach was proven to work the best. We also use it when we upgrade activeCollab installations for our customers (as part of our Professional Installation and Upgrade service).