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What Is webMethods Integration Server Clustering?
Clustering is an advanced feature that substantially extends the reliability, availability, and scalability of webMethods Integration Server.
The clustering feature uses a shared cluster store to hold webMethods Integration Server state information and utilization metrics for use in load balancing and automatic failover support. Because this activity is transparent to the client, clustering makes multiple servers look and behave as one.
Clustering in general provides the following benefits:
*Failover support. Clustering enables you to avoid a single point of failure. If a server cannot handle a request, or becomes unavailable, the request is automatically redirected to another server in the cluster.
Note:
webMethods Integration Server clustering redirects HTTP and HTTPS requests, but does not redirect FTP or SMTP requests.
*Scalability. You can increase your capacity even further by adding new machines and webMethods Integration Server to the cluster.
For details on webMethods Integration Server clustering, see webMethods Integration Server Clustering Guide for your release.
Important:
If you use pure Integration Server clustering with Adapter for SAP, the load balancing and failover mechanism of the IS cluster do not apply for Adapter for SAP RFC connections and RFC listeners. The RFC protocol has some restrictions that affect failover and load balancing:
*A (logical) RFC connection is bound to the low-level TCP/IP connection on which it was initiated, so you cannot continue and redirect an RFC connection to a different Integration Server in case the IS that started the RFC connection suddenly dies. Therefore a reliable failover is not supported for RFC connections.
*SAP Transactions that spawn over several transaction steps must be executed over the same (physical) RFC connection. Therefore reliable failover and continuation of a failed multi-step SAP transaction on a different Integration Server is not possible.
*Load balancing of inbound RFC connections is achieved by the SAP Gateway which is independent of Integration Server.
For these reasons, an Integration Server cluster does not provide benefits for SAP integration in comparison to a group of independent IS servers.