Uninstall CF2021 while CF2023 is running

That's interesting to hear your conclusion.  And of course, if it worked for you that's all that matters for your need.

But I will say first that no, there should be not inherently be any reason that the attempt to uninstall one CF version should be blocked by another that is running, since the installations are entirely separate (separate folders, separate services, separate CF admin configuration, separate jvm configuration, etc.)

Then again, when people run the CF admin of the new CF version for the first time, the "migration wizard" runs asking if they want the new CF to import admin and config settings from the previous version. In doing THAT, it's possible that some configuration in the NEW instance would "have a pointer" to a folder in the old instance.

One possibility is the listing of customtag folders. As you may know, each CF instance has its own customtags folder by default, named in the CF admin "customtags" page (under "extensions" on the left). If the path to the customtags for the old version was defined in the Admin of the new one (perhaps pulled in via that migration tool), then someone used a custom tag during the life of that new instance, perhaps that customtags folder was now "in use" by the new version.

I've also seen people have CF admin mappings in a new instance that named a folder within the old instance (that's a bit less likely to be a folder IN the old instance, since mappings are usually naming folders OUTSIDE the instance, but it's possible). Again, if someone then called a CFC in the current instance, CF could have looked through those mappings (and customtag paths) to find such a CFC, perhaps then loading it for use in memory.

In either case, it may have been that the uninstall of the old CF vresion was held up by that, such that stopping the new version would "release that hold" on such folders. And we could certainly assert that it would have been nice if SOMETHING would have informed you that it was hung awaiting that. 🙂

I'll add that a benefit of that warning also would have been that you might have then wanted to check in those folders to see if there were any files you wanted to preserve/pull into the corresponding folder of the new instance instead. That's one real negative of the "help" the migration wizard (and CAR file mechanism) offers in pulling in such settings...sometimes people are not really aware that there are files in the old instance that they are somehow unexpectedly still using.

And sadly, you uninstall may or may not have left such remnants behind. You may want to check, if the coldfusion2021 folder still remains. Generally it holds files that CF thinks are not default files (like logs, but could include such customtags, etc.)

Hope that helps. Again, I appreciate this may be a level of detail not necessary for your sitiation. I offer it as much in case someone else finds this thread in the future. 🙂