The read-only replica is a readable replica type used to read information about all objects in a partition's boundaries. Read-only replicas receive synchronization updates from master and read/write replicas but don't receive changes directly from clients.
This replica type is not able to provide bindery emulation, but it does provide eDirectory tree fault tolerance. If the master replica and all read/write replicas are destroyed or damaged, the read-only replica can be promoted to become the new master replica.
It also provides NDS Object Reads, Fault Tolerance (contains all objects within the Partition boundaries), and NDS Directory Tree Connectivity (contains the Partition Root object).
A read-only replica should never be used to establish a security policy within a tree to restrict the modification of objects, because the client can always access a read/write replica and still make modifications. There are other mechanisms that exist in the directory for this purpose, such as using an Inherited Rights Filter. For more information, see Inherited Rights Filter (IRF).