Oracle database High Availability – Data Guard, Standby, RAC

In my previous article I described some best practices in architecting database systems for first 2,5 High Availability Levels (HA) describing some technical solutions based on SAN, cluster, Clusterware, Oracle ASM, Cold Failover Cluster (CFC). This time I’ll continue till Availability level 3 describing single and cluster database solutions including Data Guard, Standby database and Oracle Real Application Cluster (RAC). I suggest reviewing a few my previous articles on database High Availability including the Availability Continuum graph that illustrates and depicts the increases in availability that can be gained with the progression between levels of availability:
High Availability and SLA requirements for Oracle database
Oracle High Availability – ASM, Clusterware, Cold Failover

Availability Level 2b: Oracle Data Guard / Standby

Another option of Level 2 availability is employing Oracle Data Guard to replicate the database to the failover hardware. Some down time is incurred during the failover to the redundant system.
At this point we consider Data Guard at one physical location. Applying Data Guard for disaster recovery solutions refers to Availability Level 4.

Oracle Data Guard provides the benefits of system-level, site-level, and data-level protection, resulting in high levels of availability and disaster recovery without loss of data. Data Guard addresses primary servers / site failures and data protection through transactionally consistent Primary and Standby databases that do not share disks, enabling recovery from server / site disasters and data corruption.

Standby database architecture consists of the following key components

–  Primary database resides on server A.

–  Standby database resides on server B. If zero data loss is required with minimum performance impact on the primary database. Read more »

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