Powerful SAP HANA HSR Questions for Success: Conquer Your Interview

Que: Does takeover takes place in case of failure of the primary?

Answer:

• If the primary SAP HANA on node 1 (either the node or the database instance) fails, the cluster initiates the takeover process.
• To automate this resource handling, you need to use the SAP HANA resource agents provided in SAPHanaSR. The system replication of the productive database is managed automatically with SAPHana and SAPHanaTopology.
• The cluster permits a takeover to the secondary site only if the SAP HANA system replication was in sync up to the point when the primary service was lost. This ensures that the last commits processed on the primary site are already present at the secondary site.

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Q: Can takeover to the secondary be done automatically?

Ans: 

By using the parameter AUTOMATED_REGISTER, you can enable automated registration. When this is activated, the cluster will automatically register a previously failed primary to become the new secondary.

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Q: What happens to the DR site when the cluster sites 1 and 2 switches?

Ans:

• This concept is known as: Autoregister the third site.
• After the HSR takeover between cluster sites 1 and 2, HANA automatically registers the third site on the new primary to maintain an HSR multitarget setup.
• To enable this, we need to set the parameter: register_secondaries_on_takeover = true.

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Want to know about SAP Cloud ALM?

Q: What is Multi-target and Multi-tier architecture?

Ans:

 Multi-tier ([A ⇒ B] → C) and Multi-target ([B ⇐ A] → C).

• Multitarget replicates data changes from the primary to multiple target systems. The additional sites are linked to the primary replication in a star topology.
• Multitier is a cascading or chained setup of HANA system replication, where the third site connects to the secondary.

Below is an example of Multi-target and Multi-tier setup:

Multi-tier i.e. A –> B (sync) –> C (async)

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Q: Can Autoregister the third site be achieved in Multi-target and Multi-tier architecture?

Ans:

In an HSR multi-tier setup, there is no automatic SAP HANA registration for the third site. You must manually register the third site to the current secondary to maintain the HSR replication chain for multitier.

Helpful Links:

https://learn.microsoft.com/en-us/azure/sap/workloads/disaster-recovery-sap-hana

https://documentation.suse.com/sles-sap/sap-ha-support/html/sap-ha-support/index.html