Figure 3 shows the main components of the database replication
environment.
The database replication process is usually done by three primary components:
??? Primary.database.server.(Publisher): The source of the data being replicated;
??? Secondary. database. server. (Subscriber): The destination of the replicated data;
there can be one of more Subscribers; and
??? Replicator: This handles sending the data from the Publisher to the Subscriber(s).
Database replication uses a snapshot of the source database to initially synchronize the databases
at the publisher and the subscriber. As transactions are committed at the publisher
side, they are captured and sent to the subscriber(s).
Transactional replication mainly is not designed for high availability; the process of promoting
the secondary server to assume the role of the primary server is manual, not automatic. In
addition, returning the primary server to its original role after a failure requires a complete
database restoration.
Database.Log.Mirroring
The database mirroring is another option that enables database-level failover against
unplanned downtime caused by server or database failures. In the event that the primary
database fails, database mirroring enables a second standby database server to be almost
instantly available with zero data loss.
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