!!! Overview
[{$pagename}] ([USN]) is a 64-[bit] [number] in [Microsoft Active Directory] that increases as changes occur provided from Local counters on every [Domain Controller].At the start of each update transaction (originating or [replicated]) on a [Domain Controller], the domain controller increments its current [USN] and associates this new value with the update request. This [{$pagename}] value is stored on an updated object in two ways for a replicated write and three ways for an originating write.

The update's [{$pagename}] value is stored with each attribute changed by the update as the local USN of that attribute (originating and replicated writes). You can use the Repadmin command-line tool to view the local USN. 
Type {{{repadmin /showmeta <object_DN >}}} 
at a command prompt and view the column labeled "Loc. USN" in the output. The maximum local [{$pagename}] among all of an object's attributes is stored as the object's [usnChanged] attribute (originating and replicated writes).For an originating write, the update's USN value is stored with each updated attribute as the originating USN of that attribute. Unlike the local USN and [usnChanged] , the originating USN travels with the attribute's value as it replicates. 
!! More Information
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[{ReferringPagesPlugin before='*' after='\n' }]