You must perform this operation on the old instance of API Gateway. For a cluster setup, you must do this on each node.

At this time, the runtime traffic is flowing to both old and new API Gateway instance. You must now stop the traffic to old instance and allow the traffic to be sent only to the new instance. But while stopping the old instance, there may be ongoing requests in the old instance which are still in progress which cannot be lost. Moreover, all the in-memory data like performance metrics, license metrics and subscription quota should be stored in the API Data Store before runtime data is migrated. This can be achieved by putting the old instance into quiesce mode with status as all.

You can see API Gateway Quiesce Mode to learn the process of enabling and disabling quiesce mode.

If the quiesce mode for all API invocation fails with an error or the status returned with a failure, you must stop the execution of the next steps and disable the quiesce mode for design time in all the nodes and bring them back to normal state. If the instances have already entered the quiesce mode, restart all the instances and update the load balancer to route the traffic only to it to go back to the original state before migration. Contact Software AG support team for help with all the relevant logs for further analysis.