"De-clustering" SAP on Windows

[jsucharski]

Hi - we have SAP installed in an HA configuration. There is one windows cluster that has SAP clustered and also SQL Server in Always On Availability Group configuration. The cluster has not been working good for us in our environment. Because of the shared disk it is more sensitive to events in our VM/SAN environment than we had anticipated.

I attempted to migrate SAP to another server ( I want to leave SQL on the windows cluster) and failed... miserably and today and rebuilding the servers from backup .

I tried following the SAP System Copy Guide instructions for Copying the Primary Application Server Instance Only(1-5 below)

With this procedure, you can move a primary application server instance to a different host within your system.Prerequisites

Central services instance for ABAP (ASCS instance) is installed.Procedure

1. Shut down all application servers.

2.Uninstall the old primary application server instance.

3. On your target host, start the installer as described in the installation guide for your SAP system at https://help.sap.com/sltoolset Area System ProvisioningGuide for Installation of Systems Based on SAP NetWeaver 7.1 and Higher.

4.On the Welcome screen, navigate to the following folder according to the requirements of your target system:<Product><Database>System CopyTarget SystemDistributed System or High-Availability SystemBased on <Technical Stack>Primary Application Server Instance.

5. After the installation has finished, restart all additional application server including the instance services.

Question then is has anyone ever gone from a HA configuration to Distributed? And if so, how?

Thank you!

Jennifer

[karl-heinz_hochmuth]

Hello Jennifer,

if I understand you correct, then you have a Windows Failover Cluster with two cluster nodes which are running virtualized on VMware or Hyper-V?

For some reasons you had problems with the shared disk of the ASCS in the past and now you want to move all SAP applications to other VMs?

My recommendation:

Add two additional application servers on Windows hosts (virtual machines) to this scenario. Then you have 4 application servers in your system, one PAS on a cluster node, one AAS on a cluster node, two more AAS on other Windows hosts.

Next step: Stop AAS on cluster node, set the related service to disabled.

Then, stop the PAS on the cluster node, and change one of your AAS to a PAS. The procedure is described in SAP note 112266, see chapter "6. Loss of a cluster node". You still have your cluster node of course, but the chapter discusses the necessary changes to convert a AAS to PAS. It's not very much work.
When done, disable the service of the PAS on the cluster node.

At this point, only the ASCS instance is left.

My recommendation:

The ASCS is configured to work using a virtual hostname. The virtual hostname and it's IP address is configured in Failover Cluster. As long as it is there, you cannot install another ASCS in parallel (using same hostname and IP address!).

Did you already installed a single ASCS on a Windows host? (distributed installation)

It just takes some minutes to complete. So it's sometimes faster to stop the ASCS on a maintenance weekend, install another ASCS using this virtual hostname on another Windows host (see SAP note 1564275) and start up your system again. You have to copy manually additional files from the cluster shared disk to the new ASCS instance (e.g. profile files ...).

Do be honest, I haven't used SAP systemcopy procedure to "copy" a clustered ASCS instance to a Windows host (distributed scenario). Sometimes it's faster to install it new.

Best regards,

Kalle

[jsucharski]

Thank you for your reply. We were able to get the procedure I had listed. Even though in the SWPM we were selecting the database server, we had to enter the info into the new default profile file and that got us past the point where the install was failing (with an error that had nothing to indicate it was db connection).

Jennifer