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It's normal in that everyone has these items occur on their lots, even in completely isolated hoods with no Maxis content. Why it does these isn't known yet. It's solely my opinion that certain items, when placed on the empty lots, will generate unknown sim references and save them to the lot files. If you plan to share the properties, you can choose to get rid of the following items in SimPE to make your property "leaner" for folks to download, and to may have less worry about with corruption of their neighborhoods:

- Sim Information (SIMI)
- Sim Relations (SREL)
- SimDNA (SDNA)
- Sim Wants and Fears (SWAF)
- SimScores (SCOR)
- FamilyTree

I could even recommend removing all jpg/tga/png Image (IMG) files except for that with Instance 0x35CA0002 to make your lot leaner for upload. The game will generate new IMG files when a change is made to your lot afterwards. Note that you must keep the Texture Image (TXTR) files, due to items on your lot referencing these (such as walls, or custom paintings). Do not delete the TXTR files.

Keep in mind, however, that even by removing the items listed above in the lot file, there may be other places in the lot file that contain references to Sims, even though there are none in your neighborhood. It doesn't mean they will corrupt your neighborhood, they could be benign. Yet there's no guarantee that removing only these references will insure a 100% corrupt-free neighborhood. These are still research in progress matters based on the newest methods tested out.

And after doing that, you have to load the lot one more time, make at least 1 structural change (rotating a tree is enough) and save. Then you're good to go. The game resets the time, the current state, etc. So all broken objects get repaired, etc.

Oh, and those unknown sim references - they link to the universal sims (ie Grim Reaper or Hula Zombie). And because every neighborhood does have these universal sims, your lot won't corrupt the neighborhood.
It will only corrupt the neighborhood if it's linked to a sim who does not exist in the other neighborhood.

You could also remove unnecessary text string files to clean the lot.



That's not true!
It's been almost two years since I started with this sim reference research. Originally here and then continued here. I was discussing with Mootilda about this subject. Mostly in PMs.

But Mootilda passed away. So I was left alone with this thing. After a couple of attempts and experiments I found out the mystery behind the sim references in TS2 lots.
The truth is, it's not the sim references that corrupt the neighborhood, not the used objects, not the previous sims, it's the leftover sim relationships that corrupt the neighborhood. Every lot has sim references. Also the never ever occupied ones. There's still a reference to the universal sims in never ever occupied lots. But as I said above, if it's a sim from another neighborhood that does not exist in the new neighborhood, the game reads the reference, cannot link the reference to a character file and that's why Mootilda's HC is throwing an error. And that's actually the thing that corrupts the neighborhood.
But if you remove the relationships and the sim information, the HC does not throw an error = no corruption = safe to move between neighborhoods.

By deleting the Sim Information file, you're deleting the entire lot history. I could prove this by removing sim references from a lot with broken objects. All of those objects got repaired at once. It was night when I last played that. But after deleting the references, the time got reset to Monday 8 am. Also the object prices reverted to their original price. So, everything gets reset and it's like it has never been played.

Some things need to be removed manually, though. (Like custom paintings, gravestones, photo booth pictures) But they can be removed before the family moves out.
So I'd say it's 100% safe to move a cleaned lot to another neighborhood. There isn't really a difference after you removed the lot history.

Again, it's NOT the used objects that cause corruption. It's the leftover sim relationships, DNA, etc. that cause corruption once they're placed into another neighborhood and once the sim whom these references link to does not exist in the new neighborhood.

Don't worry about those sim references. You can delete the references if you want. That would make the file size a little bit smaller.

The reason I had the opinion that certain objects created Sim References has to do with how a completely empty lot has none. Then by placing some objects, sim references are created. Why is that?

Here's an example. Place a 2x3 empty lot on the ground of a no Maxis content neighborhood. Save the lot. Open the lot file with SimPE, you'll find there's no SREF files. Then, go back to the game, place a fridge. Save the lot again. Open SimPE and examine the lot. There's 2 sim reference files created. Why did the fridge need it? That's an answer I'd like to know of.

I wasn't refuting that removing those items from your method, Jawusa, was not a good thing. I just said that it may not be 100% corrupt-free so as to prevent a liability issue from occurring. Meaning that even with all the research done, there may be things that can be changed in the future that we don't know of right now in the present. Perhaps it would take years to find out if even one thing about this method needs changing. It's better to mention that this research has shown that this method of removing leftover sim references is the best known method of reducing lot corruption so far, but that the possibility of other lot corruption from the files we don't have access to could still be present.

Just tossing this out there. After you have removed the references and open the lot to make one change, isn't there a chance your sim references will come right back? I am thinking more of unplayed community lots here, those with NPC creating objects.

That's how my lot generated a makeover NPC, by going live for a split second while saving. So while I did remove the references in SimPE I would not put it past the possibility that it just remade them even if the NPC is not there when you reopen the lot. On another lot I built I have not seen an NPC but the chef stove produced steam and the fountain ran and froze.

When building the hotel, I placed it in the bin. Then I placed one in a spot to take screenshots - and bartenders, waiters, etc. all over the place.
I placed a second copy then - no NPC in sight.
Not sure I will get my head around how this works at all

@joandsarah77 A sim reference will not come when you don't place any new objects. So, rotating a tree won't create a sim reference. But even if it came, it would link to one of the universal sims.
Also if you place fridges, if there's no sim on the lot, it will be a sim reference to one of the universal sims. And because they're in every neighborhood, these kind of sim references are harmless.

It's only dangerous if a sim is on the lot when you placed the fridge or any other objects. (Including off-world loiterers, visitors, and NPCs that get sometimes spawned on community lots)

As for the NPCs on community lots, they disappear if you quit without saving and load the lot again. Then you should be able to build without worrying about a NPC that may sneak into the lot package.
You can also go to the Characters folder and see if there's a new character file there, if there's one, quit without saving. You'll see that it gets removed when you quit without saving.

Once you place at least one thing and save the lot with the NPCs afterwards, you'll get plenty of sim relationships.
But you'll get less (or no) sim relationships when you place the same thing in the other lot with no NPCs.

They are not sim relationships but object relationships, SimPE shows them both as the same.
Most times that sim interacts with an item a relationship with the item and the sim's object ID is formed (see global 0x0110, Standard Entry). Some items like the standard timer will also form relationships with other items. These relationships are not stored in the neighbourhood file but the lot, sim relationships always use their neighbour ID. There is no chance of any of those things getting into the neighbourhood file and although it is a good idea to clean those things from a lot before uploading you won't harm anyone's game if you're not sure how to.

Chris, what about when you have built a lot and the NPC item has spawned a sim? Are the sim references in SimPE sim relationships then?

Ah, thank you Chris, that makes sense. I knew something was unusual with the way SimPE treats SREL files. So it's not just a relation between Sims, it can also be so with lot objects relating to Sims, or objects relating to other objects.

Not if it's in the lot file, Most items like bars will create a relationship with the NPC on generating them (see 'Bartender - Make from Template' in any bar for example).

@Chris Hatch

What about scripted scenarios? Are they also included as references in the lot? Because I'd like to move the Summerdream house into Pleasantview but I'm not sure whether removing the references will also remove the party scenario, so that's why I'm asking.

The party will not continue.
The Game Scripting (Controller - Game Scripting, group 0x7F6B4A0E) recognises when to run by Neighbourhood ID then Lot ID then the sim's GUID, if any don't match then it marks that lot as 'done' and never runs at that lot again, moving the lot could make all three not match. However the only scripting for that party is to adjust the motives of some sims and display the message "The party is already underway, and Puck's sweetheart Hermia is here! He wants that First Kiss, and now is the perfect time to make his move." the rest of the party is handled by the Party Controller. The Party Controller contains the op-code 'import lot' which should cause it to self-delete if you move it to another 'hood. Moving the lot to a different 'hood means none of the guests could be there (so the scripted message would be meaningless if it did run) and the party controller would lose track of who's party it is. It's better that it does self delete so you can start a fresh party with new friends.