SAP HANA 2.0 SPS 03 What’s New: High Availability – by the SAP HANA Academy

Introduction

In the upcoming weeks, we will be posting new videos to the SAP HANA Academy to show new features and functionality introduced with SAP HANA 2.0 Support Package Stack (SPS) 03.

The topic of this blog is high availability.

For the previous versions of this blog, see

• SAP HANA 2.0 SPS 02 What’s New: High Availability
• SAP HANA 2.0 SPS 01 What’s New: High Availability
• SAP HANA 2.0 SPS 00 What’s New: High Availability
• SAP HANA 1.0 SPS 12 What’s New: High Availability

For the full SAP HANA 2.0 SPS 03 blog list, see

• What’s New with SAP HANA 2.0 SPS 03

What’s New?

SAP HANA System Replication Playlist

On the SAP HANA Academy, there is a full playlist covering all aspects of system replication:

SAP HANA Academy – SAP HANA System Replication playlist

SAP HANA System Replication

Multitarget System Replication

As of SPS 03, the primary system can now replicate data changes to more than one secondary system. Different disaster recovery scenarios apply, depending on whether just the primary or the whole data center experiences a failure.

For the documentation, see

• Multitarget System Replication
• Disaster Recovery Scenarios for Multitarget System Replication

Invisible Takeover

In a regular takeover scenario, all connections to the clients on the primary system are lost and there is no awareness of any previous client connection on the secondary host.

SPS 03 introduces invisible takeovers, which enables the client to keep the connections to the primary system and to restore its sessions on the secondary system. However, only read transactions are supported. When the ongoing transaction is a write transaction, the session won’t be recovered.

his is configured through the use of the enable_session_recovery parameter.

For the documentation, see

• Invisible Takeover

Secondary Time Travel

It is now possible to start the secondary system in online mode on a previous point in time. Secondary time travel can be used to quickly access again data, which was deleted in the original system.

Time travel on the secondary host is only possible in the operation modes logreplay or logreplay_readaccess.

The retention time is set with the timetravel_max_retention_time parameter in global.ini, section system_replication. For time travel to work, log and snapshots are kept online in the data area and you need to set the parameter carefully to avoid log full or disk full situations.

hdbnsutil -sr_timetravel --startTime=<startTime> 
[--callTakeoverHooks=on|off].

For the documentation, see

• Secondary Time Travel

Alert 106 – ASYNC replication in-memory buffer overflow

Alert 106 is raised when the local in-memory buffer in the ASYNC replication mode is running full indicating possible network issues with the connection to the secondary system.

For the documentation, see

• SAP HANA System Replication Alerts

Host Auto-Failover Parameters

Host Auto-Failover is a built-in, fully automated high availability solution for recovering from the failure of an SAP HANA host, introduced in SAP HANA 1.0 SPS 09.

SPS 03 adds two new parameters for host auto-failover.

• enable_master_failover – defaults to true; when set to false the check of the nameserver master candidates is disabled
• startup_error_restart_retries – defaults to 4; defines the number of retries if a service fails in the startup procedure

For the documentation, see

• Host Auto-Failover Parameters
• SAP HANA – Host Auto-Failover – white paper

getTakeoverRecommendation.py

The getTakeoverRecommendation.py Python script evaluates the status of the primary system and of the system replication to help decide if a takeover is justified.

For the documentation, see

• Takeover Decision Based on SAP HANA Python Scripts

References

SAP HANA Documentation

• SAP HANA Platform 2.0 SPS 03 Features

SAP Notes

• 2551355 – SAP HANA Platform 2.0 SPS 03 Release Note

Thank you for watching

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