Oracle Tips by Burleson

Oracle Dataguard
Chapter 1 - Introduction to Oracle Data Guard

Oracle Failover Options

Replication failover – Multi-master replication can allow the RAC Grid to be open and accepting transactions, with DML cross-feeding each instance.  This requires Oracle Enterprise Edition and is only for databases with low DML rates

Real Application Clusters (2001–present) - The RAC architecture allows many instances to share a single database, but it avoids the overhead of RAM block pinging. RAC has also been enhanced to work with Oracle’s Transparent Application Failover (TAF) to automatically restart any connections when an instance fails.

Oracle Streams - This is a high-speed replication solution that takes SQL directly from the log_buffer  RAM area and replicates transactions to a remote database.  During a server crash, transactions can be quickly redirected to the replicated system.

Oracle Data Guard - This is a free option with Oracle Enterprise Edition, and it provides an automated standby database.  Upon server failure, a series of database procedures synchronizes the RAC Grid and opens it to accept connections. Oracle Data Guard is free with Enterprise Edition.

Failover and Oracle licensing

Cost-conscious Oracle shops want to know how they can get Oracle failover as cheaply as possible.  In addition to Data Guard, Oracle has a wealth of failover options, each with its own licensing costs.  Oracle has two licensing tiers, Enterprise Edition (EE) and the far cheaper Standard Edition (SE).

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