SAP High Availability and the Windows Environment
How does SAP support High Availability in Windows environments?
SAP provides an out of the box setup for windows cluster environments using the Microsoft Cluster Service (MSCS). For all other windows cluster solutions please get in touch with the specific cluster software vendor.
What is a cluster resource group?
Cluster resources are software and hardware components that are managed by the cluster software. Several resources can be grouped into resource groups. These groups are collections of resources which can be managed by the cluster service as a single unit.
Why I cannot access the shared disks when there is owned by another cluster node?
The shared disk always belongs to the cluster node which owns the cluster group at the moment. However, you should never access the SAP installation by choosing the disk drive but by using the shared name, that means “
How many failover nodes are currently supported by MSCS/SAP?
The number of SAP cluster nodes is only limited by the maximum of cluster nodes supported by MSCS. For Windows Server 2003 the maximum is 8 cluster nodes which mean 7 failover nodes. When using the SAP Replication Server with a cluster configuration the number of nodes is currently limited by two nodes.
How can I initiate a failover on MSCS manually?
On MSCS, failovers can be initiated for testing purposes manually. You can open a command prompt a type in “cluster res
What is the "Threshold"?
Within MSCS the term Threshold is referred to the number of failures before a resource fails over to the second cluster node. Please note that if you are using the Replication Server it is very important to set the “Threshold” to “0”. Otherwise the replication will not work.
Are there other cluster environments available for the Microsoft Windows platform?
SAP supports an out of the box installation for the Microsoft Cluster Service. However, there are also additional cluster software vendors for windows.As in UNIX environments these setups are handled by the partner.
Where can I find additional information regarding the Microsoft Cluster Service?
Internet
“Guide to Creating and Configuring a Server Cluster under Windows Server 2003”
“Clustering Services” - general introduction to MSCS
“Step-by-Step Guide to Installing Cluster Service”
“Technical Overview of Windows Server 2003 Clustering Services”
“Windows 200 Clustering Technologies” - information for W2K clustering services
Clustering Technology Community
Books
“WINDOWS NT Microsoft Cluster Service,” by Richard R. Lee ISBN: 0-07-882500-8
“Implementing SAP R/3 using Microsoft Cluster Server,” by David V. Watts, Mauro Gatti, Ralf Schmidt-Dannert ISBN: 0-13-019847-1
“Tuning Microsoft Server Clusters: Guaranteeing High Availability for Business Networks,” by Robert W. Buchanan, Robert Buchanan ISBN: 0071417397
“Windows Server 2003 Clustering & Load Balancing”, by Robert Shimonski ISBN: 0072226226
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