Stretch DB allows the moving of historical or less frequently needed data dynamically and transparently to Microsoft Azure. Data is always available and online, and you don't need to change queries in your solutions; SQL Server takes care of the location of data and combines retrieving data from the local server and remote Azure location. Therefore, you can completely delegate your cold data to Azure and reduce storage, maintenance, and implementation costs of an on-premises solution for cold data storage and availability. However, there are many limitations to using Stretch DB and most OLTP tables cannot be stretched to the cloud—at least not without schema and constraint changes. Stretch Database brings maximum benefits to tables with historical data that is rarely used. You can calculate the price for data storage and querying against the Azure database and decide whether you would benefit from using the Stretch DB feature.
In the next chapter, you will learn about temporal data...