Sccm collections system ou not updating
Each one targets a specific object type (Computers, Users, Groups, Active Directory) : Discovers computers in your organization from specified locations in Active Directory.In order to push the SCCM client to the computers, the resources must be discovered first.
This is very useful if you have multiple AD Site and Subnet, instead of creating them manualy, use this method to do the job for you.
You can specify to discover only computers that have logged on to the domain in a given period of time.
This option is useful to exclude obsolete computer accounts from Active Directory.
Here’s the official discovery methods definition from Technet : SCCM discovery methods identifies computer and user resources that you can manage by using Configuration Manager.
It can also discover the network infrastructure in your environment.
You also have the option to fetch custom Active Directory Attributes.