Data Guard on OCI Database Cloud Services

Hello Everyone

I'm scratching my hands by the wish I have to get something wrote about Dataguard on OCI Database cloud services.

So, I would like to share a few thoughts about how OCI handles DR needs using Dataguard features.

Data Guard and Active Data Guard provide disaster recovery (DR) for databases with recovery time objectives (RTO) that cannot be met by restoring from backup. Data Guard automatically synchronizes the primary database and all standby databases by transmitting primary database redo - the information used by every Oracle Database to protect transactions - and applying it to the standby database.

Active Data Guard extends Data Guard capabilities by providing advanced features for data protection and availability as well as offloading read-only workload and fast incremental backups from a production database. Active Data Guard is included in the Extreme Performance Edition and Exadata Service.

In order to configure a Data Guard system across regions or between on-premises and Oracle Cloud Infrastructure DB systems, you must access the database host directly and use the DGMGRL utility.

Oracle recommends that the DB system of the standby database be in a different availability domain.

The standby databases in Oracle Cloud Infrastructure Database are physical standbys.

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Data Guard Networking Requirement

Properly configure the security list ingress and egress rules for the subnets of both DB systems in the Data Guard association to allow TCP traffic to flow between the applicable ports. Ensure that the rules you create are stateful (the default).For example, if the subnet of the primary DB System uses the source CIDR 10.0.0.0/24 and the subnet of the standby DB system uses the source CIDR 10.0.1.0/24, create rules as shown in the following example.

The egress rules must enable TCP traffic only for port 1521, which is a minimum requirement for Data Guard to work. If TCP traffic is already enabled on all of your outgoing ports (0.0.0.0/0), then you need not explicitly add these specific egress rules. Service Gateway can provide NW connectivity.

Data Guard Configuration supported from Console  

The Console allows you to enable a Data Guard association between databases, change the role of a database in a Data Guard association using either a switchover or a failover operation, and reinstate a failed database.

When you enable Data Guard, a separate Data Guard association is created for the primary and the standby database.

You can use OCI web console to perform following operations

Enable Data Guard 

Perform a database switchover

Database failover

Reinstate a database

Terminate a Data Guard association

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What is Switchover?

A switchover is a role reversal between the primary database and one of its standby databases. A switchover guarantees no data loss. This is typically done for planned maintenance of the primary system. 

During a switchover, the primary database transitions to a standby role, and the standby database transitions to the primary role. The transition occurs without having to reenable either database.

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So, Failover, what that means?

A failover is when the primary database (all instances of a RAC primary database) fails and one of the standby databases is transitioned to take over the primary role. Failover is performed only in the event of a catastrophic failure of the primary database, and there is no possibility of recovering the primary database in a timely manner. Failover may or may not result in data loss depending on the protection mode in effect at the time of the failover. This operation is supported from the Standby database.

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Finally, what is Reinstate?

Reinstate – In some situations, the primary database can go into a failed state, which becomes irrecoverable. The reinstate allows customers to reinstate a failed primary database as a standby database after repair.

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It's very important to keep in mind that standby databases in Oracle Cloud Infrastructure Database are physical standbys. For cross-region Data Guard associations, only the maximum performance protection mode is supported.

The Oracle Cloud, by principle, has the mission to provide us all necessary automation to bring us more ease to manage environments with this specific needs.

Many more details about DG protection modes, standby databases concepts, as well how redo transactions transport works, I would recommend a deep dive in Oracle Documentation. 

Wish you all health and peace,

Best Regards!