!!! Overview
[{$pagename}] is a [Flexible Single Master Operation] and a [Domain Controller] responsible for processing [Relative IDentifier] ([RID]) Pool requests from all [Domain Controllers] within a given [AD DOMAIN]. 

[{$pagename}] is also responsible for removing an object from its [AD DOMAIN] and putting it in another domain during an object [Moddn]/[Modrdn].When a [Domain Controller] creates a [Security Principal Object] such as a user or group, [{$pagename}] attaches a [Unique Identifier] called the [Security Identifier] ([SID]) to the object. This [SID] consists of a [Domain SID] (the same for all SIDs created in a domain), and a [Relative IDentifier] ([RID]) that is unique for each [Security Principal Object] [SID] created in a [AD DOMAIN].Each Windows [Domain Controller] in a domain is allocated a pool of [RIDs] that it is allowed to assign to the [Security Principal Objects] it creates. When a [Domain Controller]'s allocated [RID] pool falls below a threshold, that [Domain Controller] issues a request for additional [RIDs] to the domain's [{$pagename}]. The [{$pagename}] responds to the request by retrieving [RIDs] from the domain's unallocated [RID] pool and assigns them to the pool of the requesting [Domain Controller]. There is one [RID] master per domain in a directory.

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [Active Directory FSMO roles in Windows|https://support.microsoft.com/en-us/help/197132/active-directory-fsmo-roles-in-windows|target='_blank'] - based on information obtained 2018-07-10-