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clustering for PAS (primary application server)

Dear Gurus,

We have clustering for DB & ASCS using node1 & node1. so the DB and ASCS are safe without SPOF.

We have issue with PAS. couple of time PAS node went down and users were not able to connect.

Anyone has done clustering for PAS?. Is there any SAP note available?

Thanks

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4 Answers

  • Posted on Oct 21, 2018 at 07:56 AM

    Hi Mohamed.

    Could you share the details about current cluster configuration, OS & SAP details?

    Regards

    SS

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  • Posted on Oct 21, 2018 at 03:53 PM

    Hello Mohamed,

    You should not add the PAS to the cluster.

    What should be done is to install AASs (Additional Application Servers) and ocnfigure the SAP GUI of the end users to logon using load balance.

    Thus, if any instance goes down, the user can logon again and they will reach an instance that is up and running.

    Regards,

    Isaías

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    • Hello Mohamed,

      The ERS is the "Enqueue Replication" instance.

      Confirm that the system has an ASCS instance.

      This is where the Enqueue and the Message Server should be running.

      The ASCS should be in the cluster, so if the active node fails, the cluster moves the ASCS to the cluster node where the ERS was running.

      This way, users will still be able to logon using logon groups and the Enqueue lock table would not be lost.

      Take a look at this SAP help page for more details.

      Regards,

      Isaías

  • Posted on Oct 22, 2018 at 03:59 AM

    Hello Mohamed Buhari,

    What you need is Additional Application Server.

    Once you have multiple APP server you will not face this issue.

    ------------------

    Installation looks like below

    ------------------

    CI in cluster

    DB in Cluster

    0PAS standalone

    1AAS standalone

    2AAS standalone

    ------------------

    One of the application server go down you can still access SAP system.

    Make sure you have logon group configured for your servers and also SAP guy have login through logon group

    Hope this helps

    Thank you

    Yogesh Patel

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  • Posted on Oct 23, 2018 at 10:25 AM

    >>Anyone has done clustering for PAS?. Is there any SAP note available?<<

    As you have ASCS (separate) and DB in cluster then there is no need to have another cluster for the PAS. However, there is no condition that PAS cannot be on a cluster. Having a cluster for the PAS means you have another node which is not active and used only in the event of the failover. You basically pay for the cluster solution and for having another node. What you can do here is have another App server installed on a separate node and add the new instance to the logon groups. You get the benefit of load balancing here. The advantage is you will have two App servers and you only pay for an additional node and not for the cluster. In the event of the PAS crash you will still have the AAS running and the users will be able to reconnect there. When you say the PAS goes down often, it appears to me that the system is not sized properly to handle the load so maybe you should get a proper sizing done for the system.

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