Database replication overall structure
Primary
Database
Server
Replicator
Secondary
Database
Server
Secondary
Database
Server
Initial
Synchronization
:
SNAPSHOT
NEW
TRANSACTIONS
Rada deh & Al-Ameed
Copyright ?© 2007, Idea Group Inc. Copying or distributing in print or electronic forms without written permission
of Idea Group Inc. is prohibited.
The server load and server failure problems can be addressed by replicating the database
servers to form a cluster of peer servers that coordinate updates. If the primary server
fails, applications can switch to the replicated copy of the data and continue operations.
Database replication is different from file replication, which essentially copies files. Database-
replication products log selected database transactions to a set of internal replicationmanagement
tables. The software then periodically checks these tables for updated data and
moves the data from the source to the target systems while guaranteeing data coherency and
consistency. Many database-replication products even have built-in tools to allow updating
the primary database with any changes that users made to the backup database while the
primary database was offline.
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