Best Practices to Ensure SAP High Availability

Adding high-availability capabilities to your SAP ERP system is essential to safeguard day-to-day business operations. Only then can you recover quickly in the event of an application or server failure, power outage, or natural disaster—and sufficiently protect the application and the associated data.

For IT teams planning to deploy or reconfigure high-availability for their SAP systems, there are several best practices to follow. This article provides a rundown of some of the key capabilities to implement that increase the configuration flexibility of SAP systems in order to make sure end-users, customers and vendors can all access the ERP services they rely on to conduct business.

Utilize Multiple Cloud Zones to Remove Single Points of Failure

One of the primary objectives of any high-availability architecture is to ensure that any single points of failure are eliminated, such as cluster nodes connecting to a single SAN. If you are running SAP in the cloud, you can take advantage of your cloud provider’s availability zones, which may exist in different geographic regions. Although a high-availability cluster can be deployed within a single zone, the zone itself is a single-point-of-failure. If the zone becomes unavailable, end users may lose access to the entire cluster.

The best practice is to separate cluster nodes across two zones. The SAP application can then failover from one to the other. It’s also a good idea to deploy a witness node in a third zone, which helps you avoid split-brain scenarios for high-availability clusters and comply with disaster recovery requirements.

From an availability standpoint, designing the SAP landscape to avoid any single points-of-failure also prevents any impact on application performance and enables the application to operate within SLAs. Other key SLA impacts to discuss with your cloud provider are instance sizing, infrastructure design, security, and network requirements.

Avoid Resource Constraints and Protect Lock Tables

Another key factor to check when designing an SAP high-availability cluster is the impact of your resources allocation constraints. You don’t want performance to be negatively affected by resource allocation constraints across cluster nodes.

To meet this need, the common best practice is to deploy separate high-availability clusters for each SAP instance and their associated databases. This allows for maximum performance for both the application and the database—rather than forcing each one to fight over resources on the same cluster. For businesses that use a memory-intensive database like SAP HANA, applying this best practice is especially important.

Another vital process is managing SAP instances so they are brought online and configured to communicate in a coordinated manner. For example, the Enqueue Server instance should be able to maintain the database lock table. This prevents collisions by concurrent users.

This step is critical because if the Enqueue Server goes down, no database transactions can take place. And if you can’t recover the lock table after a failure event, all database transactions in progress during the failure will be lost.  

So be sure to maintain an Enqueue Replication Server instance on a separate cluster node from the SAP Central Services instance. This node will hold a replicated back-up copy of the lock table that the Enqueue Server can use to recover its active locks after a failure. 

In a scenario such as this, the high-availability software you utilize must also keep the SAP Central Services and Enqueue Replication Server instances running on separate nodes in order to ensure data redundancy. It’s crucial to orchestrate failovers in this manner so the lock table can be recovered and all in-progress transactions can pick up where they left off.

 Ensuring High Availability When Working with Cloud Providers

If your SAP ERP platform already operates in the cloud, or if you are considering migrating from on-premises to the cloud, establish clear SLAs with your cloud provider. For example, agree on which level of application high availability you require: Is 99.99 enough, or do you need to go all the way to 99.9999?

While service level policies for many cloud providers address instance availability, they do not guarantee application availability. Check to see what your provider offers.

Following all of these tips should enable your IT team to add configuration flexibility that reduces the complexity of high availability for your SAP ERP system. At the same time, you can minimize downtime, eliminate data loss, and maintain data integrity—the keys to ensuring smooth day-to-day operations for your business.