In SQL Server, connections and sessions are fundamental concepts that play a crucial role in how clients interact with the database server. Let’s break down each concept:
Connections:
- A connection represents the communication pathway between a client application and the SQL Server instance.
- When a client application connects to SQL Server, it establishes a connection through a network protocol (such as TCP/IP, named pipes, or shared memory).
- Connections are managed by the SQL Server Database Engine and are typically created and destroyed as needed by client applications.
- Each connection has its own set of resources and settings, including authentication credentials, session settings, and access permissions.
- Connections consume server resources such as memory and CPU, so it’s essential to manage them efficiently to avoid resource contention and performance degradation.
Sessions:
- A client application establishes a connection to SQL Server, it initiates a session to execute queries and perform database operations.
- Sessions maintain state information about the client’s interaction with the server, including transactional state, temporary objects, and session-specific settings.
- Each connection may have one or more associated sessions, depending on factors such as connection pooling and multiple active result sets (MARS).
