Data migration is one of the most important operations to be performed during upgrade. Data migration is performed in two phases. In the first phase, the old instance of API Gateway is blocked for core design time data updates and all the core design time data is migrated to the new API Data Store, while the new API Gateway instance is running. After this, the new instance is restarted with the migrated design time data and the endpoint is added to the load balancer. At this time the transactions are served by both the old and new instances. In the second phase, all the transactions to the old instance of API Gateway is blocked and the logs and events data are migrated to the new instance API Gateway while it is serving the transactions.

In zero downtime upgrade, API Gateway looks after migration of the API Data Store data only. An administrator must look after migration of the file system configurations and custom IS packages.

To upgrade API Gateway in zero downtime, the following capabilities are required.