Because of a malfunctioning UPS, I consider deleting it and recreating it from scratch.
HOWEVER I'm wondering about the impact on my users. Once it's recreated, what do they lose (alerts, stuff like that) ?
When you rebuild UPA then you lose all your existing profile information. If your profile information consists entirely of information pulled from Active Directory then it’s no big loss. That’s not the case with most farms though. Users have augmented their profile information with pictures or other information, and there’s also the whole social aspect. The UPA stores all the tags and notes and activities.
But you can preserver the many things from getting lost. You can reuse the existing UPA databases(Profile DB, Social DB, Sync DB. But before blowing up the UPA you must note down configuration settings.
After that when you delete the UPA from Central Admin, Please make sure Delete data associated with the Service Applications option is Not Checked.
Now go to SQL Server and Delete the Sync Database but Dont Delete the Profile(Stores user information and activity feed)** and Social DB**(Stores tags and notes). Both are most important.
Now Create the UPA using the existing database and complete the setup, You will all set.
When you delete UPSA, you will be provided an option "Delete data associated with the Service Applications", just remember to NOT check that option and you should be good.
The user profile service application is associated with the following databases in the backend SQL:
**User Profile Service_ProfileDB_GUID** **User Profile Service_SocialDB_GUID** **User Profile Service_SyncDB_GUID**
It's the Profile and Social databases you are concerned about.
When you recreate UPSA, for the above databases use the same names.