The Microsoft Cluster Server (MSCS) configuration is the standard switchover solution for the SAP system running on Windows platforms. In this configuration, the SAP system is installed on two nodes of a cluster. Under normal operation, the SAP central instance runs on one node and the database on the other node of the cluster. If one of the nodes fails, the affected central or database instance is automatically moved to the other node, so preventing downtime. The failover mechanism is enabled by the MSCS software and a cluster-aware version of the database management system (DBMS).
The main advantage of MSCS is to prevent downtime. It does this by replicating single points of failure – that is, the database and the central instance – which increases the overall availability of the SAP system.
The cluster is normally fully transparent to clients accessing MSCS. However, there might be a delay in the event of failure due to failover.
Alternative Cluster Solutions
If you want to install a different form of clustering or high availability solution, contact your SAP partner, who will arrange installation and support.
We only support standard configurations and might require you to deinstall other high availability solutions if you require support.
For more information on SAP support for MSCS, see SAP Note 106275.
For more information on combining MSCS with the Microsoft SQL Server Standby Database, see Comprehensive Microsoft SQL Server High Availability Solution.
To use SAP Cluster on Windows, you must meet the following prerequisites:
· Enterprise Edition (EE) of SQL Server 2000
· Hardware certified by SAP and approved by Microsoft for MSCS
· SAP data stored on RAID1 and RAID5 disks
For more information, see the installation documentation for the SAP system.
SAP recommends you not to use “Active-Active” configuration of MSCS, in which two SQL Servers coexist on the same cluster.
With SAP Cluster on Windows, SAP offers a standard high availability solution for the SAP system on all supported hardware platforms. To achieve this, SAP uses the cluster capabilities of MSCS.
Performance during normal installation is comparable to a distributed installation but can drop significantly after failover.
High availability in MSCS operates on the following levels:
· Hardware replication
Since the server is physically replicated, all internal machine components are replicated. This includes motherboard, memory, Disk controller, power supply, NIC, bus, and so on. If any of these fail, the system can fail over and still continue functioning.
· Automatic failover
Failover occurs rapidly without manual intervention, so no time is lost manually working out the cause of the problem and deciding how to fix it.
During operation of SAP Cluster on Windows platforms, MSCS monitors the system for failure and switches over services in the event of a failure. Both monitoring and switchover occurs automatically, that is, without operator intervention. However, the system administrator is still responsible for solving the problem that led to failure (for example, replacing faulty hardware components).
SAP Installation documentation for Windows (choose the version for your database) on SAP Service Marketplace at:
Cluster Server Concepts and Architecture from Microsoft at: