As all you know many changes has been made on SharePoint Server Application Services. The Search Service Application and also the User Profile Synchronization Service has been many many times improved on the new version of SharePoint.

  

The classic User Profile Synchronization Service Application ( SharePoint 2010 and SharePoint 2013 ) uses still and always the FIM to get any data from Active Directory to fill our profiles.

But now, on the new version with SharePoint 2013 there is something called “Direct Active Directory Import
The main novelty lies into the synchronization of properties of users in the corporate directory (Active Directory only) with the ability to import it directly.

So concrete? The direct import can synchronize the SharePoint user profiles with Active Directory without using Forefront Identity Manager (FIM), as was the case with SharePoint 2010.
To explain it as simple possible: “Direct Import from Active Directory which is designed to import the AD profile as quickly as possible.”

Are the benefits??? A bigYES”.. Not using FIM :-) ! Witch Administrator has never had a problem with this service application? Problems with the “Starting” User Profile Service Applications? .. It’s all over now
But there are also some limitations:

  • Mapping to system SharePoint properties is not supported.
  • Mapping two different AD attributes to the same SharePoint property is not supported

How it works? The direct import works without starting the Synchronization Service in SharePoint (which is used for communication with FIM configuration)! Actually, the Direct Import services are based on User Profiles.

Configure the type of import, configure the connection to the directory and then run the Syncronization ... And that’s all.

According to that article, the following script snippet can be used to enable AD Import mode in SharePoint Server 2013: Only the OU setting is removed when you run the Remove-SPProfileSyncConnection cmdlet in SharePoint Server 2013

$UPSA=Get-SPServiceApplication -Name "<User Profile Service Application Name>"
$UPSA.NoILMUsed=$true
$UPSA.Update()

The User Profile Replication engine is a optional component of SharePoint Server 2010 and is part of the SharePoint Administration Toolkit. It replicates User Profiles and social data between User Profile service applications.

The User Profile Replication Engine ( UPRE ) who was a separate download tool comes as an out-of-the-box feature on SharePoint Server 2013
It comes very handy when you have a Development, Q&A and Production environment. In stead of building it all again from scratch, you can replicate all or some user profiles.

For more information please read and refere to: http://www.harbar.net/archive/2012/07/23/sp13adi.aspx