I encountered a really odd situation installing MC 16.0.49 alongside MC15. In my case, it made MC16 uninstallable, until I devised a workaround. Probably my situation is unusual, but I'm explaining it here in case anyone has a similar experience, and because I hope MC can become a tad more informative and controllable when "Upgrading".
Details: I started MC16 installation, it declared it was "Upgrading" so I wandered off to do something else. THREE HOURS later I noticed it was still "Upgrading", with constant disc I/O.
Digging a bit, I discovered MC seemed to be copying my entire MEDIA library -- all the music files -- from where I keep them on drive M to C:\Documents and Settings\USERNAME\Application Data\J River\Media Center 16\Library. That's a non-starter, because the location MC picked is too small. There is no place on this computer with enough space to duplicate the entire set of media files. This computer has 2 drives, C and M. Drive C is 250GB, used for Windows, apps, etc. Drive M is 750GB, used solely for MC library, which is about 500GB (about 80 thousand files split among 3 libraries) and growing. (Backup of library is to external drives.)
But even if the duplicate library would fit "somewhere", I didn't see why MC16 would need to do this. I assume the LIBRARY files are different and can't be shared between MC15 and MC16, given the stated addition of "relational" fields. But why would MC need to copy the MEDIA files too?
MC16's "Upgrading" on my machine was doomed to fail when it filled up the drive. There was no evident "abort" option. So I crashed out of MC's installation, hoping the program was installed and I could deal with the library later. But it seems the library and media files are all copied FIRST, and only then is the app actually installed (that seems backwards). Given the apparent need to duplicate all the media files, there seemed to be no way to install MC16 on this computer.
But duplicating all the files seemed "wrong", not likely to be MC's normal behavior. Perhaps something was goofing up MC16's "Upgrading" logic.
I devised a workaround, which solved my problem, and lets me guess at the cause.
I have several libraries in MC15, three with my real media, and the original Default that I don't use. So which MC15 library did MC16 decide to use? Likely either the current active library or the one named Default.
If MC16 looked at my MC15, noted the current active library, and proceeded to copy it, that would explain the massive copying because that one library has more than 300GB of media. Maybe that's what happened.
OR, maybe MC16 simply copies the MC15 library known as Default, a library I don't intentionally use. I don't have my "real" library at the default location, and it is NOT called "Default".
To cover both possibilities, I opened MC15 and selected the original Default library to make it current. This revealed that it has a bunch of stuff in it, perhaps from an MC15 installation where it decided to scan my drive for media files. I didn't notice because I never use the Default library. I deleted all the library entries, then put 7 songs in it.
Because my drive C was now almost full, I deleted the 200GB of of library/media files the prior installation attempt had already copied to it (the real files are still on drive M).
Then I restarted MC16's installation process. IT WORKED! Installation finished in less than one minute. The new MC16 library has only the 7 songs. This time, it did NOT copy the actual media files; the library entries point to the files on drive M.
So why did it try to copy all my main library's media files from M to C during the first installation attempt? One guess is that MC16 did not use the current active MC15 library, it used the Default MC15 library, which in my case had lots of tracks. I didn't pay any attention to those listings, just deleted them, so now I don't know where they pointed. But maybe something about them led to MC16 doing a massive copying to where it thinks they should be. The copying is the puzzling part, because MC16 could find the real media files -- otherwise it couldn't have copied them. So why not just use them where they were located on drive M?
I'm hoping someone can confirm WHAT library MC16 uses in MC15 to do its "Upgrading" -- the current active library, or the Default library? Assuming it's the Default, it would be nice to understand what could cause all that copying.
Suggestion: It would be really nice if MC's installation, when it involves an existing library, could tell the user ALL the major steps it is about to do, and then give Proceed/Cancel (and perhaps other options such as "Select the desired library and location"). If it had said "Using MC15 Default library", then said "MC15 Library and Media files will be copied to MC16 library location C...", and maybe even stated the quantity and size of the files in the library, I could have realized something was amiss the first time, and been confident of a good outcome the second time.
And/or maybe there's just a bit too much "Upgrading" automation. The process could be in two separate user-controllable steps:
Step 1: Install MC16 and license it. Install a Default library, but don't populate it.
Step 2: Allow the user to populate the Default library by scanning and/or manually adding media -- OR let the user open an existing user-selectable library (with a notice that it will be imported/recreated/whatever).
Perhaps do Step 2 after a long pause (like the auto-scan for media process), or perhaps wait for a user response or action selection.
PS: Some might say my joyride would not have happened if I used Default as my main library, so it had valid records pointing to valid media. I used to do this (been using MC since version 7), but years ago someone on this board recommended not using the Default library or location, because it is subject to "stuff happening". Aside from today's "Upgrading" adventure, I continue to think this is good advice,.
