Chapter 1. Overview 1.1. Introduction Cost-Optimized deployments of SAP S/4HANA systems play an important role in S/4HANA migration scenarios, especially in saving costs related to additional nodes. It is also critical if such systems are to be made highly available, in which case, the constraints need to be correctly configured. A typical Cost-Optimized setup for SAP S/4HANA High-Availability consists of 2 distinct components: SAP S/4HANA ASCS/ERS cluster resources Database: SAP HANA with System Replication Please refer to Automating SAP HANA Scale-Up System Replication using the RHEL HA Add-On , for more details. This article focuses on the setup of SAP S/4HANA HA environment where both SAP HANA System Replication and the ASCS and ERS instances are managed by a single cluster. This is done using the RHEL HA add-on and the corresponding HA solutions for SAP, available as part of RHEL for SAP Solutions. Note : Below is the architecture diagram of the example installation of a 2-node cluster setup which this article focuses on, with a separate section on the design and configuration of the additional SAP HANA instances with System Replication. Note that ASCS or SAP HANA primary instances can failover to the other node independently of each other. 1.2. Audience This document is intended for SAP and Red Hat certified or trained administrators and consultants who already have experience setting up highly available solutions using the Red Hat Enterprise Linux (RHEL) HA add-on or other clustering solutions. Access to both SAP Service Marketplace and Red Hat Customer Portal is required to be able to download software and additional documentation. Red Hat Professional Services is highly recommended to set up the cluster and customize the solution to meet the customer's data center requirements, which may be different than the solution presented in this document. 1.3. Concepts This document describes how to set up a Cost-Optimized, two-node cluster solution that conforms to the high availability guidelines established by SAP and Red Hat. It is based on Standalone Enqueue Server 2 (ENSA2), now the default installation in SAP S/4HANA 1809 or newer, on top of RHEL 8 for SAP Solutions or above, and highlights a scale-up SAP HANA instance that supports fully automated failover using SAP HANA System Replication. According to SAP, ENSA2 is the successor to Standalone Enqueue Server 1 (ENSA1). It is a component of the SAP lock concept and manages the lock table. This principle ensures the consistency of data in an ABAP system. During a failover with ENSA1, the ASCS instance is required to "follow" the Enqueue Replication Server (ERS). That is, the HA software had to start the ASCS instance on the host where the ERS instance is currently running. In contrast to ENSA1, the newer ENSA2 model and Enqueue Replicator 2 no longer have these restrictions. For more information on ENSA2, please refer to SAP OSS Note 2630416 - Support for Standalone Enqueue Server 2 . Additionally, the document will also highlight the SAP HANA Scale-Up instance, with fully automated failover using SAP HANA System Replication, where the SAP HANA promotable clone resources will run on each node as per set constraints. This article does NOT cover preparation of the RHEL system for SAP HANA installation, nor the SAP HANA installation procedure. For fast and error-free preparation of the systems for SAP S/4HANA and SAP HANA, we recommend using RHEL System Roles for SAP . Configuration of both is considered as a Cost-Optimized SAP S/4HANA with an Automated SAP HANA Scale-Up System Replication Environment. 1.4. Support Policies Please refer to Support Policies for RHEL High Availability Clusters - Management of SAP S/4HANA and Support Policies for RHEL High Availability Clusters - Management of SAP HANA in a Cluster for more details. This solution is supported subject to fulfilling the above policies.

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