How Does sp_reset_connection Prepare SQL Server Connections for Reuse?

Unveiling the Intricacies of sp_reset_connection: A Comprehensive Guide

Within SQL Server's connection pooling mechanism, the intricate stored procedure sp_reset_connection plays a crucial role in ensuring that connections retrieved from the pool are appropriately prepared for reuse. Yet, its inner workings remain shrouded in mystery. Let's delve into the specifics of sp_reset_connection, exploring its multifaceted functionalities and limitations.

What sp_reset_connection Does

Upon reusing a connection from the pool, data access API layers like ODBC, OLE-DB, and SqlClient invoke sp_reset_connection. Its purpose is to restore the connection to a "clean slate" before it embarks on new tasks. This entails:

• Reseting error states and numbers (e.g., @@error)
• Terminating child threads executing parallel queries
• Patiently awaiting the conclusion of pending I/O operations
• Releasing buffers and memory allocated by the connection
• Erasing temporary tables and worktables
• Terminating global cursors and SQL-XML handles
• Closing system and user tables
• Discarding temporary objects
• Aborting open transactions
• Releasing locks and handles
• Resetting SET options to defaults
• Reinitializing @@rowcount and @@identity values
• Deactivating session-level trace options

What sp_reset_connection Doesn't Do

Amidst its extensive reset capabilities, sp_reset_connection refrains from altering the following:

• Security context: Connection pooling relies on matching connections based on exact connection strings, preserving the user's security context.
• Application role: Application roles cannot be reverted, so their association with the connection persists.
• Transaction isolation level: This remains untouched.

In conclusion, sp_reset_connection acts as an invisible custodian, ensuring connections retrieved from the pool are thoroughly cleansed of previous operations, allowing them to seamlessly fulfill their new responsibilities. However, it does not interfere with certain fundamental connection properties, such as security context and transaction isolation level.

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