HP-UX Directory Server 8.1 deployment guide

Figure 6-10 Replicating chained databases
6.4.4 Schema replication
In all replication scenarios, before replicating data to consumer servers, the supplier server checks
whether its own version of the schema is synchronized with the version of the schema stored on
the consumer servers. The following conditions apply:
• If the schema entries on both supplier and consumers are the same, the replication operation
proceeds.
• If the version of the schema on the supplier server is more recent than the version stored on
the consumer, the supplier server replicates its schema to the consumer before proceeding
with the data replication.
• If the version of the schema on the supplier server is older than the version stored on the
consumer, the server may return many errors during replication because the schema on the
consumer cannot support the new data.
A consumer might contain replicated data from two suppliers, each with different schema.
Whichever supplier was updated last wins, and its schema is propagated to the consumer.
WARNING!
Never update the schema on a consumer server, because the supplier server is unable to resolve
onflicts that occur, and replication fails. Schema should be maintained on a supplier server in a
replicated topology.
If the standard 99user.ldif file is used for custom schema, these changes are replicated to all
consumers. If there are custom schema files, ensure that these files are copied to all servers after
making changes on the supplier. After all the files have been copied, restart the server.
See “Creating custom schema files” for more information.
The same Directory Server can hold read-write replicas for which it acts as a supplier and
read-only replicas for which it acts as a consumer. Therefore, always identify the server that will
function as a supplier for the schema, then set up replication agreements between this supplier
6.4 Using replication with other Directory Server features 91