How to patch a SAP Application Pacemaker Cluster

SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server for SAP Applications 12

If there is a need to update the nodes of a cluster one can do a rolling update.
 

First it should be checked that the SAP Application is in good state. A Hana should be in Sync Ok state, a Netweaver having the ERS up and connected for example. Contact the SAP Administration on this.
Second that the cluster itself is in an idle state, no pending changes waiting to be applied on the cluster level. This can be validated by issuing

   crm_simulate -L -S

which should show empty Transition Summary like

   Transition Summary:

   Executing cluster transition:

Once this is established on one node issue

    crm cluster stop
    
this will failover all relevant resources to the other node.

After this is done, any patching can proceed without consideration for SAP nor the Cluster on the node that got the cluster stopped.

Once the patching is done, maybe even a reboot, on the patched node the cluster is started again with

   crm cluster start
   
This will make the node available again for SAP Applications.

Care should be taken, that any SAP Application is started correctly and is working properly on the returning node. Especially any SAP Hana Secondary should be in

   Sync OK
   
status. It is necessary to check that the failover is available again.

If for example a Primary Hana was stopped, it will now be in a failed start unless AUTOMATIC_REGISTER was set to true. In this case it would be necessary to register the former Primary as new Secondary according to the documentation. Just like if a failover had happened.

After establishing that the Application as well as the Cluster are fine, the same process is repeated with the other node.

   crm cluster stop
   
patching, maybe reboot and then with

   crm cluster start

reintroduced into the cluster.