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The SAP Application Server High Availability Interface Certification, a.k.a. SAP Application Server HA-Interface Certification, is to ensure the communication between SAP Applications and 3rd-party cluster solutions. A solution with this certification will avoid a split-brain situation where a cluster will not try to interfere with planned maintenance tasks carried out by the SAP administrators. Without the HA Interface, when an SAP administrator stops an SAP application that's running in a cluster, the cluster will interpret it as a failure and thus try to remediate. The result is disruptive to the planned maintenance tasks.

The communication is enabled between the HA-interface (cluster API) of SAP Start Service (sapstartsrv) and 3rd party cluster connector, as illustrated in the image below.

SUSE's Distinguished SAP Architect Fabian Herschel has explained the technical details in this blog: Using sap_vendor_cluster_connector for interaction between cluster framework and sapstartsrv

SLE15 has been certified both NW-HA-CLU_750 and S/4-HA-CLU 1.0 for SUSE Linux Enterprise Server for SAP Applications 15.

There are slight differences between the two certificates:

Certificate Certified OS Version Certified SAP Kernel Supported Databases Standalone Enqueue Server Number of Nodes in the Cluster
NW-HA-CLU_750 SUSE Linux Enterprise Server for SAP Applications 15 Netweaver 7.50+ SAP ASE, Oracle, IBM DB2, MaxDB, HANA DB Standalone Enqueue Server 1 (ENSA1) Only 2 nodes
S/4-HA_CLU 1.0 SUSE Linux Enterprise Server for SAP Applications 15 S/4HANA 1809 HANA DB 2.0 Standalone Enqueue Server 2 with the Enqueue Replicator 2 (ENSA2) 2 nodes or more

Both certifications are applicable to multiple platforms, from bare metal, virtualized environment, to public cloud, where SUSE Linux Enterprise Server for SAP Applications 15 and High Availability Extension are supported.

Customers now benefit from a certified start/stop infrastructure within the HA setups, can establish a unified management interface, and simplify the management of the maintenance tasks such as a rolling kernel switch (RKS).

Without this HA-Interface, it’s difficult to perform maintenance to SAP instances running inside a cluster. For example, if SAP sys admin needs to restart the SAP ASCS/ERS instances, there are two options to do it:

  1. Use pacemaker cluster management interface crm or crm_gui to stop or start the instances through the resources.

  2. Put the cluster into Maintenance mode, then stop and start the instances using SAP MMC/MC, or sapcontrol, or other tools. After maintenance tasks are complete, exit the cluster Maintenance mode.

The problems with either methods are that, in a lot of datacenters, the cluster and SAP instances are managed by different teams, respectively, thus in order to stop/start SAP instances, the SAP sys admin has to go through a complex process to get the support from the cluster administrator. With this HA-Interface in place, when the SAP sys admin stops the SAP instances, cluster will standby and not to interfere. So, it eases the operations.

For example, the ASCS resource, that’s managed by a cluster, has a status “Started”:

Now the SAP sys admin stops the ASCS instance through SAP Management Console:

The ASCS instance is stopped:

In the cluster, the ASCS resource has a “Stopped (disabled)” status because the cluster recognized that it’s an intended operation thus didn’t interfere.

As you can see, because of the HA-Interface integration, by using the same SAP Management Console, SAP sys administrators can independently perform the maintenance tasks that require stop/start the SAP application server instances that are running in a cluster. This feature greatly simplifies the operational process and provide flexibility and stability to the environment.

For details on how to enable the HA-Interface in your cluster, please refer to the following documentations:

  1. SAP NetWeaver Enqueue Replication 1 High Availability Cluster - Setup Guide for SAP NetWeaver 7.40 and 7.50, section 3.4

  2. SAP S/4 HANA - Enqueue Replication 2 High Availability Cluster - Setup Guide, section 3.4

If you have any questions, please feel free to ask questions in the comments section.
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