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90 CHAPTER 6: MANUALLY CONFIGURING MULTI-MASTER REPLICATION
Multi-Master
Replication
Overview
Multi-Master Replication (MMR) is the process of copying and
maintaining database tables in multiple databases that make up a
distributed database system. Changes applied at one site are captured
and stored locally before being forwarded and applied at each of the
remote locations.
Oracle replication is a fully integrated feature of the Oracle server; it is not
a separate server. 3Com recommends and only supports MMR, which is
comprised of multiple master sites equally participating in an
update-anywhere model. Updates made to an individual master site are
sent to all other participating master sites.
Some advantages to MMR include:
■ Supports highly available data access by remote sites.
■ Provides data that is updated frequently and propagated
automatically.
■ Allows real-time data propagation.
■ Can provide failover protection.
When you set up MMR, the databases to be replicated must be in the
same state. If, for example, database A has been populated with
provisioning data and database B is empty, you can set up replication
between A and B but A’s data will not be copied to database B. In this
case, you must back up database A and restore it on database B, then set
up replication (see Backing Up and Restoring the Authentication and
Directory Server Database).
Replicated Table
Location
The tables located in the /opt/3com/VCX/vcxdata/db/vcxdata/bulkload
directory are automatically replicated.
These tables make up the VCX Authentication and Directory Services
database schema.