Chapter 14. Unique UID and GID Number Assignments
An IdM server generates user ID (UID) and group ID (GID) values and simultaneously ensures that replicas never generate the same IDs. The need for unique UIDs and GIDs might even be across IdM domains, if a single organization uses multiple separate domains.
14.1. ID Ranges
The UID and GID numbers are divided into ID ranges. By keeping separate numeric ranges for individual servers and replicas, the chances are minimal that an ID value issued for an entry is already used by another entry on another server or replica.
The Distributed Numeric Assignment (DNA) plug-in, as part of the back end 389 Directory Server instance for the domain, ensures that ranges are updated and shared between servers and replicas; the plug-in manages the ID ranges across all masters and replicas. Every server or replica has a current ID range and an additional
nextID range that the server or replica uses after the current range has been depleted. For more information about the DNA Directory Server plug-in, see the Red Hat Directory Server Deployment Guide.