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New Enqueue Replicator in Failover Cluster environments

In this blog, I will show you the new Enqueue Server 2 in conjunction with the new Enqueue Replicator. You will learn the differences to the old Enqueue Replication Server (ERS) and the changes in the operations concept.

NetWeaver based HA configuration

NetWeaver-based systems use the two executables “enserver.exe” (Enqueue Server) and the “enrepserver.exe” (Enqueue Replication Server). Here are two example screens:

ASCS instance (#00) in a Failover Cluster:

 

ERS instance (#10) in a Failover Cluster (installed on each cluster node locally):

 

In this configuration, the ERS instance which does not run on the same host where the ASCS instance is running connects to the Enqueue Server and starts the replication of the lock table.

Lesson learned: The ERS connects to the Enqueue Server.

 

New concept, starting with S/4 HANA 1809

SWPM 2.0 uses the new executables and concept for S/4 HANA 1809 installations or higher. The executables are “enq_server.exe” (Enqueue Server 2) and “enq_replicator.exe” (Enqueue Replicator). Here are two example screens:

ASCS instance (#00) in a Failover Cluster:

 

ERS instance (#10) in a Failover Cluster (now clustered like the ASCS!):

 

The main difference of the new concept is that now the Enqueue Server 2 starts a connection to the Enqueue Replicator and initiates the replication of the lock table.

Lesson learned: The Enqueue Server 2 connects to the Enqueue Replicator.

To be able to do this, the ASCS profile must contain the (virtual) hostname of the Enqueue Replicator instance.

For more information on how to configure new Enqueue Server 2 and Enqueue Replicator instances, visit the SAP Help Portal.

SWPM 2.0 installs and configures this automatically.

If you upgrade from a NetWeaver-based system with the SAP SUM tool, be aware that SUM can upgrade the system, it’s configuration, and the profiles, but is not able to change the configuration in Failover Cluster!
See this important SAP Note: 2639281 – “Migration to Standalone Enqueue Server 2 in Windows Failover Cluster environments”

The new concept has big advantages for HA scenarios with more than 2 cluster nodes. The ERS is now a clustered instance. SWPM automatically configures a so-called “affinity” in the Failover Cluster to prevent the cluster to operate both cluster groups (ASCS and ERS) on the same cluster node. Only if there is just one cluster node left, the cluster will bring both cluster groups online.

You can check the affinity with these PowerShell commands:

(Get-ClusterGroup -Name “SAP <SID>”).AntiAffinityClassNames
(Get-ClusterGroup -Name “SAP <SID> ERS”).AntiAffinityClassNames

The result must be in both cases the same affinity name. All cluster groups that belong to this affinity, will not be brought online on the same cluster node. With just one exception: if there is just one node left.

In Failover Cluster Manager you now see two cluster groups:

ASCS:

ERS:

Important!
Do not change the name of these cluster groups!


Depending on the installation method you have chosen in SWPM, the cluster group for the ASCS instance may contain additional cluster resources, like a shared disk and File Server resource.

The Enqueue Replicator instance will be installed locally (in SAPLOC), as the old ERS instance before.

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