Hello,
Like a good boy I did some research and read FAQs/WIKIs before posting, but I didn't find
what I was looking for, so here I am.

I like to think about myself as an expert TS3 user, but, you know, you can't know everything
and I'm pretty rusty with the game, not to mention that when I used to play regularly I didn't
linger much with the same savegame, so I have little or no experience with this kind of issues.
Anyway, I'd like to have a confirmation on what happens in a generic situation, but I'll make a
specific example to help you understand exactly what I mean (and mostly to help myself to explain it clearly).

So, here it the situation. Let's say you installed the violin premium content from the store,
which is an objects that, among other things, adds a skill to the game. Now, this skill can
be considered an alien, a stranger, because it does not really make part of the game
(as a manner of speaking), so the game is less "protected" (as opposed to a skill that
comes with an EP for which there is specific code and data structures) in case it gets removed.

Sorry for the long introduction, I'm not good at keeping my speechs short.

Now let's say you have played with the violin and also some non selectable Sims have
used it and hence learned the related skill (keep in mind that a Sim may have learned a
skill even if it doesn't appear in his/her skill tab - that only shows those where at least level 1
was achieved, presuming they are not hidden-skills).

Now let's say that you move your household on other worlds multiple times (could be various
transfers combined with back and fort from/to vacation/UL worlds) and let's say that in those
other worlds too there are Sims (again, outside your household, and this may be especially
the case for those who play more than one) that used the violin and hence learned the skill.

I hope it's all clear so far.

Now, let's say that the violin is boring you and for some reason you want to uninstall it
AND keep playing the same savegame(s). In case you don't know then let me tell you:
the game won't like that!

Now, I have an idea on how to deal with this situation, but I'd like to have a confirmation
of the steps to take and that uninstalling the violin wouldn't lead to corrupted savegame(s).
What I'm especially concerned about is: even if you can make sure that the current world
a savegame is based on is safe to use, what happen if you visit back one of the worlds
where your household has been, will the Sims there still know the - now non existent - skill?
(it gets especially ugly if you load a game where Sims where currenctly using interactions
based on that skill/object while the game was saved).

Another question, this very naif: what happen when you go back in a world where your
household has already been previously? Have local Sims aged? Would you find them
the way you left them? (I don't think so because it's not like you are loading a savegame
based there, but I'm not sure how it works).

If you have no personal experience with the violin itself, just think about another premium
item that adds a skill, even an hidden one (the climbing wall perhaps? hey, that's probably
even a better example because Sims will use the object and acquire the skill even without
having it in their inventory).

I've no personal interest whatsoever in knowing the answer, I'm just asking for a friend...

Longwinded and detailed as your post is I am still not quite sure what your actual question is or rather what your question is in addition to the answer to your question that you provided yourself. Removing a skill and then going back to a save that made use of that skill sounds tricky and I can well imagine the save to corrupt then.
However, mods like ErrorTrap seem to have some clean-up routine that can effectively deal with this. At least I haven't seen any big warning sign with regard to the KamaSimtra module, which adds a custom skill, too, of the NRaas WooHooer mod that you should never uninstall it once it's been used.
But that's about as far as my experience goes with that kind of thing.

The only thing I know from personal experience in addition is what happened when I removed the Tree of Prosperity premium content from my existing games. Without ErrorTrap they would all be completely FUBAR. The thing with Store premium content is that even if you uninstall it, a lot of their scripts are still in-game, either through the core, the Content Patches or the ccmerged package.

Now this is the actual reason for my reply. What do you mean by going back to a world? You cannot move between worlds in EA default, so your question doesn't make a lot of sense under these circumstances because you always go back to a save and therefore to the state that save was in when you left it.
But you say that you are not going back to a save so I am not sure what you mean or what methods you have in mind for "going back". I have a few things in mind that could be what you mean but if I went through all of them without really knowing what it is that you actually want to do or achieve, my post would be as long as yours

Thank you, you handsomely avatared user :P
(not sure what that means, if anything, but in my head it sounded cool and was a compliment)

Oh, so the "Transfer/Move to..." cellphone interaction comes from a mod (I use AwesomeMod and
a bunch of NRaas mods that may be responsible for that, but I was sure that was a game feature)?

EDIT: wait, it is a game feature and also a basegame one. But I probably explained that poorly
in my first post, so I hope that it makes more sense now. So...

PREMISE
- you start a new game in Sunset Valley
- then you move your household in another world (not using the Bin/Library as proxy, but using
the phone interaction)
QUESTION
- if you go back to Sunset Valley, in what state you'll find that? It's like starting a brand new game
there again or will your Sims still know/remember some of the residents? e.g. are relationships preserved?
what about lots you modified/created/destroyed? That may seem unrelated to the thread's topic, but
can help to understand what happens also after uninstalling things (will Sims still know the violin skill?).

Of course you can answer me to try it directly and see it for myself, but I'm super lazy and that
sounds like a drag, so I was hoping to take advantage of other users' experiences.

You always move to a new instance of that world if you use the "Move To..." option that EA provided in one of the later patches. Unless you use mods (ErrorTrap in that case) the world's .nhd file that you left will actually be deleted. So if you left Sunset Valley the old Sunset Valley will be gone and if you move back to Sunset Valley the Sunset Valley will be as if you started a new game there. The "Move To..." option is just another way to emulate the library bin moves. I think to remember that this was also said so in explanations by Gurus. They had "discovered" that the evict, move to library, start fresh game and then import from library was too complicated for some users so they provided a more "intuitive" means for the same effect.

You can keep the old .nhd only with mods, however. Traveler combined with ErrorTrap allows you to go back and forth between worlds and maintain their states as you left them. But then aging conditions are also determined by the mod.

(And now I'll have to go outside for a while to calm down my blushed, handsomely avatared ego. )

I see, that sounds as both good and bad news at the same time for me... err, for my friend.

I was just wondering why the "old" world files were kept in the savegame folder if they weren't
going to be used any more. That's ErrorTrap doing then? Probably to be used in combination
with Traveler. Interesting.

Last thing, then I promise I'll shut up. What about university and vacation worlds? Intuition,
more than direct experience, suggests me that with those worlds or way of travel things
work differently (turists come to mind, for instance). Like, if you go to China for the second
time it's not like going there for the first time, right? Again, I never used those features much
so I don't know and I could definitely check that by myself instead of bothering you but since
we are here and you are so kind...

How fortunate for you your friend that I have tried this, although only once, with a family that did not only have travel experience but owned a vacation home in Egypt and had family members living there. Unfortunate for you your friend, however, I only remember it vaguely. But in any case the travel destination .nhd files are being kept, you assumed correctly, and therefore also any changes you had made to and in those worlds. But as far as I remember home ownership, relationship statuses and family ties were severed and had to be reapplied/regained.

Some people use this as a method to make customisations to travel destinations and keep them for every game they play: they modify a fresh copy of the destination in a fresh game in Edit Town, save and then keep the .nhd files as templates and copy-paste them in their saves folders before they travel there. This method should not be used, however, for travel locations that have been played in already, as this can seriously mess up any new game, for obvious reasons.

What are you is your friend exactly working on, if I'm allowed to ask?

Are you? Do you know the secret handshake? No?
Then I don't know what are you talking about and I take offence at your innuendo!

Jokes aside, thank you very much. And even if I played the dumb (for some reason
that came easy to me) and lazy card, I'm actually trying those things myself, but don't
think for a split second that I was making fun of you or wasting your time, I really need
confirmations and to hear about real experiences - true stories - because I only play
for a few minutes on a test game and that is not enough to evaluate all side effects
and long term consequences

I don't want to quote Oppenheimer.

----

Here's my test and my doubts:
[CUT]
I'll save you from a boring wall of text and I'll just write the bottom line.

It's probably an obvious thing, but still. Technically, when you leave a vacation world (and I guess
it's the same for the University world) you are saving the game and overwriting the .nhd file of the
vacation world related to the current savegame (inside its folder). This means that when you go
back to that world you'll find the same "situation" (for lack of a better word) that was going on when
you left it: so if a Sim was/is performing a violin related interaction the game is screwed.
----- EDIT -----
Now that I think about it, I'm not that sure any more that the game is saved automatically
when you leave a vacation or UNI world (or any world if Traveler allows that) unless you
also save manually the game once you are back in the home world as some sort of
confirmation of the changes made and the "state" it was when we left it (until then kept into
memory or, I don't know, maybe saved as a temp file) made also in the vacation/UNI world(s).
I should test this: yep, confirmed. You have to actually save the game manually, what was I thinking?

[... the game is screwed] Maybe not beyond hope, though.

• You quit the game without saving
• backup the crap out of the savegame
• make sure you are using NRaas ErrorTrap (not sure if Overwatch does help in this scenario, but it can't hurt)
• install the violin (or whatever) again
• reload the game, go to every vacation worlds and to University - well, only on those where you've been
  while the violin was installed (or you can do this only for the world that you know is at risk and worry
  about the others only if and when you go there and see that there's a problem) and on each and every
  one of them, do this:
  • pause the game
  • reset all Sims ("ResetSim *" from the console)
  • remove all violins (this may not be strictly needed, thanks to ErrorTrap, but better play it safe)
  • remove the violin skill from every Sim that has it. You can do this easily using MC and its filters
    and setting the skill level to -1 (this may not be strictly needed, thanks to ErrorTrap, but better play it safe)
  • maybe it's a good idea to also remove opportunities/dreams/etc related to the violin from all Sims,
    but I'm not sure if MC can filter those
  • go back to the home world and save the game, repeat for the next world (but it occured to me that
    maybe this way the game will use a lot of memory and saving can become a problem, so maybe it's
    better to make one world (or as many as possible) in one session then quit the game, reload it and
    resume the cleaning
• we do the same thing in the home world: pause the game, reset all Sims, remove object+skill, remove opportunities/dreams
• save the game and quit
• uninstall the violin
• reload the game and try it

That seems to be many steps simply to get rid of some skill references. Is there any benefit in this as opposed to simply not using the object and its skills then?

Resetting a vacation or university world - or any other world, come to think of it - comes with its own risks, btw. You'll break the connection between role Sims and their respective role object, for example. Once reset they might go back to their work but the motive lock that is part of the role system will cease to work. To fix that you will either have to reset the object with DebugEnabler and reassign the role with Register or simply place a new instance of said object(s).
In university worlds this might also mess up the whole professor-students system

Resetting all Sims or a whole world is something that I only do as a very very last resort.

You mean keep the object installed but somehow stop using it (maybe disabling to use autonomously - or at all - its interactions)?
If uninstalling doesn't guarantee an uncorrupted savegame (or if you don't bother keeping the object, but then why would you uninstall
it in the first place?), I agree.



You are probably correct (I can't reply to your points for lack of first hand experience or more likely I don't remember
what happen in the cases you describe, so I'll take your word for it).

The alternative to a raw and brutal global soft reset is to check every single Sim (making them the active one,
to avoid to miss something, for instance a Sim could still be routing toward the object and you can't know what
they are about if your don't check their queue) to make sure they are not using a skill related interaction.
If a player has the patience to do that, it seems like a preferable solution.

Thanks for your input. I'm sure I haven't considered every possible facet of the problem and of the possible solutions.

Making everyone active doesn't really work in travel destinations. Well, it does work with the right mods, but I wouldn't recommend doing that.

If I had to get rid of one object in every save I would check the Object Stats with MasterController first: how many violins are in that world and where? Then I'd delete those that are in inventories first, then those outside of inventories. If you are worried that some of them might be in use you could focus on Sims that have them not in inventories and check wether they use it. Soft-resetting these might be okay. Do this in the middle of the night. Chances are lower that they use it then.

Besides, inactive Sims don't buy violins, so they have to be given one by the player. You should roughly know how many Sims received one, no?

After all violins are gone check all Sims with the skill and set these to -1, again with MasterController. That save should be clean then. Save and reload and have ErrorTrap clean everything that might be left. Save again and don't use that save until you've uninstalled the violin.

Sounds solid.

If we talk about a more generic situation (the violin after all was just an example
I used to explain what I meant), deleting a specific object is not always possible.

Well, as you link to this thread in your, not so mysterious anymore, download post and mentioned that you don't know whether you can remove a skill from several Sims at once, I'll answer here: Yes, you can. Don't count on me being exactly correct, because I am not in-game now but it goes something like this:

Click on City Hall or computer:
(1)NRaas/MasterController/Sim/Advanced/Skill Level
(2) The following pop-up list should give you several filter options for finding the Sim(s) you want to modify. Chose "Skill"
(3) The following pop-up list should now list all skills that are given in the population and the according skill levels in separate list entries, and also tell you how many Sims have a skill at each level. Choose all "Programming" entries from level 0 to level 10 (I assume that you have no level 11)
(4) Now a pop-up list should open that shows each Sim with its portrait that falls under that category. Select All
(5) a small pop-up window should appear in which you are asked to give the new skill level. Type "-1"
(6) It may be that MasterController then asks you whether it should assign that level to all selected Sims. Confirm and Done!