Database replication is the process of copying database records from one physical database to another, either of the same or different vendors. It generally takes the forms Master/Slave or Master/Master, and can be either eager/synchronous or lazy/asynchronous. In master/slave replication, updates and inserts are only permitted on the master copy, which is replicated to the slave(s). This is the most common and stable form. In master/master or multi-master replication, updates are permitted on any copy of the data, and changes are synchronized.
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