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Master and Slave Replicas

Only one replica in a cell, the master replica, accepts updates to its database from clients. Other replicas, called slave replicas, accept only reads from clients. The master replica propagates any updates to the slave replicas. For example, either a master or a slave replica can provide account information to a client program such as /bin/login. However, if you are adding an account or changing password information, those updates can be handled only by the master replica.

The process of updating the database differs slightly between the master replica and slave replicas. The following figures illustrate the master and slave update processes. The processes are described in the topics that follow the figures.


The Master Replica Update Process


Slave Replica Update Process