ERROR: Save Errors (Error 12, 13, or 16)

Problem
While saving I get the error message: Error 12 (or 13 or 15 or 16). Please see Read-Me for more information.

Meaning of the Errors
Error 12: World file save failure. Probably Memory related
Error 13: Post-save callback failure. Unclear what that means. They fixed an error that was causing this and it seems to not occur as often.
Error 15: Open failure. You probably don't have enough rights to write in the folder.
Error 16: Loose file copy failure. The file cannot be (over)written.

Avoidance & limitation of possible loss

• Since Error 12 seems to be caused by memory issues, a 64-bit operating system and at least 4 GB of RAM might help avoiding this error. EA altered the executable file with Patch 1.17/etc so that the game can allocate 4 GB of RAM. It might help to upgrade your system. Make sure ALL of your EPs are patched to the newest level or you might still see the issue.
• Make sure your Computer fulfills the minimum requirements (EAs minimum requirements are a little low, especially with all EPs) 
• Save often and in cycles (5-10 savegames with different names or use Twallan's Saver Mod to auto save.
• Regularly backup your user files.  
• Check the folder  CurrentGame.sims3 before starting the game. It should be empty. It only contains data during gameplay. If your game crashed, this folder might still contain something. Move or delete it's content.
• Make sure your saves folder doesn't contain any saves with the extension .bad. Delete those, they are unusable. 
• Increase your virtual memory
• Start your game in compatibility mode  and/or as administrator
• If you are running Direct 10 or 11 (Windows Key - R, then type dxdiag), try installing DirectX 9 as well
• Make sure you have enought room on your hard drive
• Defrag your System
• Don't play long game sessions. Quit and restart the game in between.
• If the error occurs regularly in one game but not so much in others, try cleaning your game with Twallan's Error Trap or move your sims to a new town with the porter (the mod lets you keep your relationships to all Sims you pack to move to the new town)
• CC and mods can cause all kinds of Error. Use the 50/50 Method and available tools like Dashboard or Custard to find the culprit 
• The memory system introduced with Patch 1.21/1.22 bloats your save game enormously. This can become heavy on your RAM. Delete memories for your active/inactive Sims that you don't need.

Suggestions
You can try the following suggestions while the game is running and then try saving again.

As soon as you get the error, the save is written to a folder with the extension .bad. You'll find it in your saves folder. Delete that folder before continuing.

Error 12 & Error 13 

• Use save as and a new name instead of save
• Try saving in Edit Town mode as well as live mode
• Try saving your game paused and unpaused and at different speed levels.
• Move your saves folder to the desktop
• Never use save & quit. Always save your game first and then quit the game without saving. 
• Don't use spaces or special chars in your save game names.
• If you have lots of stuff in your inventory, reduce it.
• If all fails, quit your game without saving and restore a backup.

Error 15
Error 15 occurs when you don't have enought rights to access the saves folder. Make sure you have full access to the folder your saves folder is in and it's not hidden. If nothing helps, start your game as an administrator.

Error 16
Error 16 occurs because of a file system failure which can occur if you try to overwrite a file in use or  that is corrupt. Saving as with a new name should solve the issue.

Further Reading

• Game Help:TS3 Save Errors
• Game Help:Restoring Backup Saves  
• Sims 3 & World Adventures Error 12, 13 or 16 
• ERROR: Game Crashes (CTD)