SSE Cleaning master files simultaneously is bad because?

[audiodef]

Someone recently asked me why the master files for a Bethesda game can't be cleaned all at the same time. I remember reading about this quite a while ago, but I can neither remember the reason nor readily find good information about it.

 

So for what technical reasons can't the game master files all be cleaned simultaneously? Asking to satisfy curiosity.

[cdcooley]

If you're undeleting records you can do them all at once. And honestly that's the critical part of the cleaning process because a deleted record can potentially cause the game to crash.

 

The removing duplicates part of cleaning has to be done one step at a time or there's no point in even trying. (Technically it's not critical that you remove duplicates.)

 

The various DLC files don't depend on each other. That means that a record in Dragonborn.esm can be identical to the same record in Skyrim.esm because it was copied over from Skyrim.esm. That duplicated record is almost always an error caused by the CK thinking the record was changed when it really wasn't or because some other related record was changed (and the CK has a bad habit of making copies of things it shouldn't). If you don't have any files loaded between Skyrim.esm and Dragonborn.esm then there's really not a problem with that duplicated record. But it will hide any changes to that record that mods loaded in between might try to make.

 

Assume this case:

Skyrim.esm has a record with a value of 8.

Update.esm changes the record value to 5 (to correct some problem).

Dawnguard.esm changes the record value to 6 (to balance with some other item).

Hearthfires.esm doesn't have that record.

Dragonborn.esm has a record identical to the one in Skyrim.esm.

 

When the game loads it will see the 8 from Dragonborn which is most likely wrong. If you try to clean them all at the same time it looks like the value in Dragonborn is a valid change to the 6 from Dawnguard. But if you clean them individually then the final winning record will be the 6 from Dawnguard.

 

The horrible truth is that it's possible the value 5 from Update.esm is the one that should be used or that the developers changed their mind while making Dragonborn and intentionally tried to set it back to 8 (but that is extremely unlikely). Unfortunately automated tools can't pick from a list of changes but they can handle the simple and most common case of that record from Dragonborn being an accidental copy from Skyrim (but only when you clean the master's one at a time the same way they were created).

[audiodef]

Great explanation, thank you.