How do I configure RHEL HA to manage the SAP ERS (Enqueue Replication Server) instance?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 5, 6 with High Availability or Resilient Storage Add-Ons
  • SAP with standalone ERS instance.
  • High availability using rgmanager

Issue

  • How should I configure my Red Hat Cluster so the Enqueue Server locking table is preserved across failovers?

Resolution

  • Ensure that you have enabled the central processing mode of rgmanager

    Central processing mode needs to be enabled in rgmanager, check the rgmanager man page for more details.
    In order to enable it ensure that the attribute central_processing with a value of one 1 is added to the rm tag of your cluster.conf file:

    <rm central_processing="1">

    Since rgmanager cannot transition to/from the central processing mode, you need to perform a full restart of rgmanager in all cluster nodes for this change to be applied, as described in Which configuration changes require a restart of the entire cluster?.

  • Create an event file in all cluster nodes.

    Create a file named /usr/share/cluster/event-service-ers.sl in all cluster nodes with the following content:

    notice("Event service triggered!");
evalfile("/usr/share/cluster/follow-service.sl");
follow_service("service:svc_ascs", "service:svc_ers", "service:svc_ascs");

    This will instruct rgmanager to keep scv_ascs and svc_ers services running in different nodes, and to stop the latter if only one node remains online in the cluster.

    svc_ascs and svc_ers should match the clustered services names chosen by you in cluster.conf file.

  • Add the event in your cluster.conf that points rgmanager to your event script.

    Define an event in your cluster.conf file within the rm tag, after the last service entry:

    <events>
      <event class="service" name="service-ers" file="/usr/share/cluster/event-service-ers.sl"/>
</events>

    For a more detailed setup description check the reference architecture Deploying Highly Available SAP Servers using Red Hat Clustering.

    Please, beware that the node event described in the reference architecture is not required, only the service event is required for successful management of your ERS instance by rgmanager

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