Forum OpenACS Q&A: Re: upgrade OpenACS 5.2.3 to 5.9.1, advice?
For example if you are upgrading from 5.3.2 to 5.5.1, you might think that it would upgrade all packages first to 5.4.3 and then 5.5.1. But in fact, it upgrades each package individually to 5.5.1, before moving on to the next package in the dependency hierarchy. This can cause problems e.g. imagine a scenario where you have package A before package B in the dependency hierarchy. Now imagine that package A has a 5.5.1 upgrade script, which makes a reference to a 5.4.3 feature in package B. That 5.4.3 feature won't be yet available as package B hasn't been upgraded yet, so the package A upgrade to 5.5.1 fails.