The most common use is in connection with Oracle database implementations.
Database administrators might create multiple instances of the same database for different purposes.
For example, if you sign in to an Oracle database, your login session is an instance.
SQL Server Instances
A SQL Server instance usually means a specific installation of SQL Server.
It’s not the database; instead, it’s the software used to create the database.
Maintaining multiple instances might be useful when managing server resources.
Database Schema vs.
Database Instance
It may also be helpful to think of an instance in context with adatabase schema.
The schema is the metadata that defines the database design and determines the methods for data organization.
It includes a database’s tables and their columns and any rules that govern the data.
This arrangement is the structure, or schema, of the database.
This picture includes the data and its relationship to other data in the database at a particular time.
