SQL Server, with DB instances as the smallest management units, provides a stable and reliable database service. A DB instance is an isolated database with a unique identifier. Instance types are a critical property for database service evaluation. You can select or change your instance type anytime based on your actual business needs.

The following table describes the instance types of SQL Server.

Instance Type	Introduction	Note
Stand-alone	A single-node architecture is adopted for better cost-effectiveness.	Suitable for small applications or development and test environments, which have lower cost budgets. However, if a fault occurs on a stand-alone instance, the instance cannot recover in a timely manner.
Active/Standby	The active/standby architecture is adopted for HA. Auto switchover is triggered during faults. The standby instance is invisible to you after being created.	Suitable for production environments of medium-size and large enterprises, such as enterprise IT, government, finance, and medical care services.

Relational Database SQL Server