SAP clustered resources explained in detail
You are running NetWeaver-based SAP applications on a Windows Failover Cluster. This blog will explain the details of the cluster resources’ properties and how they work together.
We start with a screenshot of a common SAP cluster group (also known as cluster “role”):
You see two SAP related resources here:
- The “Service” resource starts the SAP service (like you would start this service in Windows Service Control Manager).
- The “Instance” resource starts the SAP instance (like you would start it with SAP MMC or sapcontrol.exe)
The instance resource depends on the service resource. Both resources have similar, but different properties.
SAP Service Resource:
Service Name: That’s the name of the SAP service (see Windows Service Manager). The Syntax is by default: SAP<SID>_<Instance-Number>
Trace: You can enable an extended trace with “1”. Then, you get much more information in cluster.log. This is only necessary in case you want to analyze the problem together with SAP support.
AcceptableOfflineTime: The default value is 30 seconds which should fit for all cluster configurations. If your SAP service needs longer than 30 seconds to start, you can increase the value here.
MaintenanceMode: “0” = off, which is the default. You can turn on MaintenanceMode with “1”. This mode will be automatically set by SAP SUM tool in case you upgrade an SAP system in a Failover Cluster.
With enabled maintenance mode, the cluster will no longer check if the SAP service is online, offline, or healthy. The condition of the service will be ignored completely!
SAP Instance Resource:
This resource has more properties.
ExecuteBeforeFailure: You can enter the patch to a batch script here.
For example: c:\scripts\alert.bat. In case the resource becomes “failed”, the cluster will execute your script. With this script, you can send emails, SMS, alerts, run applications … whatever you want to get alerted!
SAPSystem: The instance number of the SAP (A)SCS instance.
HAnotRelevantApps: You can enter applications here, which will be started by SAP start service (sapstartsrv.exe), but will be ignored by the cluster. In the example above, sapcpe.exe (SAP copy app) and SAP Web Dispatcher (sapwebdisp.exe) will be started but threaten as a not relevant application for the cluster. If sapwebdisp.exe crashes, the SAP cluster group will not be affected. You can also add own application here if they’re started by SAP start service (see instance profile).
ExecuteAfterOnline: Same as ExecuteBeforeFailure, but the cluster will run a script here only if the resource was started successfully.
Trace: Same as the trace parameter of the SAP service resource.
ServiceControl: default value 1, in case you do not use the SAP Service resource, but the old “Generic Service” resource, the value is 0 here. SAP does not recommend using the Generic Service resource anymore!
SAPSystemName: The SID of the SAP system.
ExecuteBeforeOffline: Same as ExecuteBeforeFailure, but the cluster will run a script here only if the resource was stopped successfully.
Maintenance Mode: default 0. Same as SAP service parameter.
AcceptableYellowTime: This is the default value in seconds which defines the maximum time the cluster will wait for an SAP instance to become “green”. The color here refers to the colors of the SAP MMC: Yellow means, the instance is starting. Green, it is fully started.
If your SAP instances need more than 60 seconds to start, you can increase this value.
One more thing …
If you see other parameters like those above, you’re using an older cluster configuration.
Here is an example:
API Version … IgnoreYellowState … EnableInterfaceCaching … they’re not used anymore.
Possible values there will be ignored.