Configuration Considerations

Use the information in this section to plan the installation and configuration of Sun Cluster HA for SAP. The information in this section encourages you to think about the impact your decisions have on the installation and configuration of Sun Cluster HA for SAP.

Failover and Scalable Applications

• Retrieve the latest patch for the sapstart executable – This patch enables Sun Cluster HA for SAP users to configure a lock file. For details on the benefits of this patch in your cluster environment, see Setting Up a Lock File.

• Read all of the related SAP online service-system notes for the SAP software release and database that you are installing on your Sun Cluster configuration – Identify any known installation problems and fixes.

• Consult SAP software documentation for memory and swap recommendations – SAP software uses a large amount of memory and swap space.

• Generously estimate the total possible load on nodes that might host the central instance, the database instance, and the application server, if you have an internal application server – This consideration is especially important if you configure the cluster to ensure that the central instance, database instance, and application server will all exist on one node if failover occurs.

Scalable Applications

• Ensure that the SAPSIDadm home directory resides on a cluster file system - This consideration enables you to maintain only one set of scripts for all application server instances that run on all nodes. However, if you have some application servers that need to be configured differently (for example, application servers with different profiles), install those application servers with different instance numbers, and then configure them in a separate resource group.

• Install the application server's directory locally on each node instead of on a cluster file system - This consideration ensures that another application server does not overwrite the log/data/work/sec directory for the application server.

• Use the same instance number when you create all application server instances on multiple nodes - This consideration ensures ease of maintenance and ease of administration because you will only need to use one set of commands to maintain all application servers on multiple nodes.

• Place the application servers into multiple resource groups if you want to use the RGOffload resource type to shut down one or more application servers when a higher priority resource is failing over - This consideration provides flexibility and availability if you want to use the RGOffload resource type to offload one or more application servers for the database. The value you gain from this consideration supersedes the ease of use you gain from placing the application servers into one large group. See “Freeing Node Resources by Offloading Non-critical Resource Groups” in Sun Cluster 3.1 Data Service Planning and Administration Guide for more information on using the RGOffload resource type.

• Create separate scalable application server instances for each SAP logon group.

• Create an SAP lock file on the local instance directory -  This consideration prevents a system administrator from manually starting an application instance that is already running.