Azure SQL Database Tiers and License Models

Azure SQL Database is a multitenant relational database management service hosted in Azure available in two performance tiers:

• General Purpose—suitable for most business applications not requiring fast I/O or high availability
• Business Critical—best for applications requiring fast I/O and high availability.

Until Apr. 2018, all Azure SQL Database use was licensed using a Microsoft developed metric called Database Transaction Units (DTUs), which defines the power and relative responsiveness of a database as a blended measure of CPU, memory, and read-write rates. The DTU pricing structure also included licensing for the SQL Server technology used by the service, with no opportunity for existing SQL Server customers to receive a discount for licenses they already owned.

In Apr. 2018, Microsoft began offering a new pricing model, called vCore (virtual core). This model echoes how Azure VMs are licensed, because the number of virtual cores in a VM defines the size and price. The vCore model includes a set number of virtual cores, RAM, and a base storage amount. All other costs (additional storage, input/output, network egress, and backup storage) are additional.