HP-UX Directory Server 8.1 administrator guide

l=Boston,dc=example,dc=com subtree. For example, the following two attribute-value
settings are allowed:
mail=bjensen,l=Chicago,dc=example,dc=com
mail=bjensen,l=Boston,dc=example,dc=com
To ensure that only one instance of a value exists under both subtrees, configure the plug-in to
ensure uniqueness for the entire dc=example,dc=com subtree.
3.7.6 Replication and the attribute uniqueness plug-in
When using the Attribute Uniqueness Plug-ins on Directory Servers involved in a replication
agreement, carefully consider how to configure the plug-in on each server.
Consider the following cases:
• Simple replication with one supplier and one or several consumers.
• Complex replication with multiple masters.
Attribute Uniqueness Plug-ins do not perform any checking on attribute values when an update
is performed as part of a replication operation.
3.7.6.1 Simple replication scenario
Because all modifications by client applications are performed on the supplier server, the Attribute
Uniqueness Plug-in should be enabled on the supplier. It is unnecessary to enable it on the
consumer server.
Enabling the Attribute Uniqueness Plug-in on the consumer does not prevent Directory Server
from operating correctly but is likely to cause a performance degradation.
3.7.6.2 Multi-master replication scenario
In a multi-master replication scenario, the masters act both as suppliers and consumers of the
same replica. Because multi-master replication uses a loosely consistent replication model,
enabling an Attribute Uniqueness Plug-in on one of the servers is not sufficient to ensure that
attribute values will be unique across both supplier servers at any given time. Therefore, enabling
an Attribute Uniqueness Plug-in on one server can cause inconsistencies in the data held on each
replica.
However, it is possible to use an Attribute Uniqueness Plug-in, providing both of the following
conditions are met:
• The attribute on which the uniqueness check is performed is a naming attribute.
• The Attribute Uniqueness Plug-in is enabled on both supplier servers.
When these conditions are met, attribute uniqueness conflicts are reported as naming conflicts
at replication time. Naming conflicts require manual resolution. For information on how to
resolve replication conflicts, see “Solving common replication conflicts”.
144 Creating directory entries