SharePoint 2013 peoplepicker works differently across site collections

Question

Our SharePoint 2013 on-premise farm is installed on DomainA.com. DomainA have form one-way trust with DomainB.com. We have setup user profile sync for both domains. But we didn't configure our people picker to handle DomainB.com.

From my understanding, all people picker would not able to query for any users under DomainB. Even I type in correct AD login ID (e.g. DomainB\userA), the people picker should return "No exact match was found".

However, on the same farm, site collection A can add two users DomainB\userA & DomainB\userB. On site collection B, only Domain\userA can be added (userB return no exact match error). On site collection C, both users cannot be added and return No exact match error.

Site collection A and B was migrated from a SharePoint 2010 farm. Site collection C is newly created. The old 2010 farm have been discarded so I cannot check the old settings. Why is it?

Answer 1

When user type something in people picker, according to my understanding, will query from 3 sources. They are:

• Client side's cache (Seems it is recorded at HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\LowCache\Extensible Cache\DOMStore. You may simply open browser in privacy mode can get rid of this)
• Configured domain controller
• User Information List

As mentioned, I have not configured people picker to handle DomainB.com. Hence it is not querying from domain controller. I compared the User Information List of 3 site collections.

Site collection A have both users in list. SC B have only 1 user. SC C do not have both users.

So how come the users are added to A and B site collections? I guess the users have joined the survey or discussion board built under site collection A & B. Whenever there is an update/delete occur, SharePoint will add the users into User Infomration List.

Tested in our environment and proved it is correct. Thanks!