# HA/DR operations
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## Oracle Data Guard
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You can use manual failover or switchover to the standby database using steps described in the [Switchover and Failover Operations](https://docs.oracle.com/en/database/oracle/oracle-database/19/dgbkr/using-data-guard-broker-to-manage-switchovers-failovers.html#GUID-44E7A982-7CD4-4A51-B00E-62C0698C5CD6). You can also automate this process by following the steps in [Oracle Data Guard Fast-Start Failover](https://www.oracle.com/technetwork/articles/smiley-fsfo-084973.html). When using this feature with the observer node, you must place the observer node in the third Availability Zone. Ensure that you have the license to use the fast-start failover, it may not be included with the Data Guard. You can also use supported third-party products that provide automatic failover operation with the Data Guard. To reconnect the SAP applications post-failover, see the *Reconnect SAP instance to database* section-premises in https://www.sap.com/documents/2016/12/a67bac51-9a7c-0010-82c7-eda71af511fa.html.

![Data Guard Broker switch over](http://docs.amazonaws.cn/en_us/sap/latest/sap-netweaver/images/fig8_odg-hadrops-orc-sap-nw-lx.png)


## Perform a DNS change
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In case of manual failover, you may install SAP application servers using a virtual hostname and perform a DNS change to direct the SAP application servers to the new primary database server. For a DNS resolution in Amazon, you can use any of the following options.
+  [Amazon Route 53](https://docs.amazonaws.cn/Route53/latest/DeveloperGuide/dns-configuring.html) enables you to create a private hosted zone for your environment and an A record for the virtual hostname used for Oracle database. Initially, this A record is mapped to the IP address of the primary Oracle database instance.
+ You can maintain your own DNS server on-premise or on your Amazon EC2 instances. You can create an A record there for your virtual hostname used for Oracle database. Initially, this A record is mapped to the IP address of the primary Oracle database instance.
+ With the [Amazon Directory Service](https://www.amazonaws.cn/directoryservice/), you can create an A record for the virtual hostname used for Oracle database.

With any of the previously mentioned options, you can change the A record to a private IP address of the primary database instance in case of a failover. This DNS change can also be automated using Amazon services and scripts.