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Chapter 3. HA Solution for S/4HANA based on ABAP Platform 1809 or newer
3.1. Standalone Enqueue Server 2 (ENSA2)
Standalone Enqueue Server, a component of Application Server ABAP, is a mechanism to ensure the high availability of the lock table and its entries.
Standalone Enqueue Server has evolved into generation 2 since NetWeaver 7.51, known as Standalone Enqueue Server 2, or ENSA2. In ENSA2, if the ASCS fails, it can start on a separate node in the cluster, and copy the lock entries from the enqueue replicator 2.
In ABAP platform 1809 or newer, the Standalone Enqueue Server 2 (ENSA2) has become the default installation.
3.2. Supported Scenarios
| Supported Scenario | Description |
|---|---|
| Multi-node cluster | Because in ENSA2 ASCS doesn’t have to “follow” ERS, that makes a multi-node cluster possible |
| Two-node cluster | Upgraded two-node cluster can easily adjust the setup to switch from ENSA1 to ENSA2 |
Brand new installations can take this chance to design the architecture, choosing between multi-node cluster or two-node cluster. Below is the architecture diagram of a typical 3-node cluster. Of course more nodes can be added upon customer’s datacenter requirements or needs.
3.3. Support Policies
Please refer to Support Policies for RHEL High Availability Clusters - Management of SAP S/4HANA.
3.4. Configuration Guides
- On-Premise: Configuring HA clusters to manage SAP NetWeaver or SAP S/4HANA Application server instances using the RHEL HA Add-On
- AWS: Configure SAP S/4HANA ASCS/ERS ENSA2 on Amazon Web Services (AWS)
- Azure with GlusterFS: Azure Virtual Machines high availability for SAP NetWeaver on Red Hat Enterprise Linux with GlusterFS
- Azure with NetApp: Azure Virtual Machines high availability for SAP NetWeaver on Red Hat Enterprise Linux with Azure NetApp Files for SAP applications
- Azure with NFS: High availability for SAP NetWeaver on Azure VMs on Red Hat Enterprise Linux with NFS on Azure Files
- GCP: HA cluster configuration guide for SAP NetWeaver on RHEL
- IBM Power System Virtual Server: Configuring high availability for SAP S/4HANA (ASCS and ERS) in a RHEL HA Add-On cluster
3.5. Cost-Optimized SAP S/4HANA HA setup (HANA System Replication and ENSA2 combined)
With current versions of S/4HANA, it is also possible to run HANA and ABAP Application Server instances on the same system. This makes it possible to have a "cost-optimized" S/4HANA setup where both HANA System Replication and ENSA2 are managed by a single cluster running on the same cluster nodes.
For more information, please refer to Configuring a Cost-Optimized SAP S/4HANA HA cluster (HANA System Replication + ENSA2) using the RHEL HA Add-On.
