Starting with Version 4.5, all OpenACS core packages support automatic upgrade. That means that, if you have OpenACS 4.5 or better, you should always be able to upgrade all of your core packages automatically. If you haven't changed anything, no manual intervention should be required. If you are running OpenACS prior to 4.5, upgrading will require manual effort.

It's always a good idea to precede an upgrade attempt with a snapshot backup.

OpenACS consists of files and a database schema. The files in a new tarball include database upgrade scripts. To start the upgrade, replace your existing files with the new files and then browse to the APM, which will detect the new packages and offer to run the appropriate database upgrade scripts. After restarting the server again, the upgrade is complete.