Update schema while new data is coming in

Hi,

we are having a web application that ist o be online availyble 7x24. We plan for the scenario that the application needs a software update (new tables , modified tables et. al.) Management and customer requires that the application is still running while the upgrade goes on. How would you solve this, that you have one server with the old schema where new data is coming in, meanwhile another server is brought up to latest release. And data of the old server (or delta of data) will be send to new server. We will propably have 2 servers anyway because of the traffic. Please help me with your ideas.

Regards
Antje Stejskal

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