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sql-server-extended-events-engine.md

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title Extended Events engine
description The Extended Events engine enables the definition of events and processing of event data, manages Extended Events, and maintains a list of sessions.
author WilliamDAssafMSFT
ms.author wiassaf
ms.reviewer randolphwest, dfurman
ms.date 10/22/2023
ms.service sql
ms.subservice xevents
ms.topic concept-article
ms.custom
ignite-2025
helpviewer_keywords
extended events [SQL Server], engine
monikerRange =azuresqldb-current || >=sql-server-2016 || >=sql-server-linux-2017 || =azuresqldb-mi-current || =fabric-sqldb

Extended Events engine

[!INCLUDE SQL Server Azure SQL Database Azure SQL Managed Instance FabricSQLDB]

The Extended Events engine is a collection of services and objects that:

  • Enable the definition of events
  • Enable processing event data
  • Manage Extended Events services and objects in the system
  • Maintain a list of Extended Events sessions and manage access to that list

The Extended Events engine itself doesn't provide any events or actions to take when an event fires. The processes that use the Extended Events engine define interaction with the engine. These processes add event points and supply the actions to take in response to event firing.

The following illustration shows a simplified view of an Extended Events session. For more information, see Extended Events sessions.

:::image type="content" source="media/detailed-extended-event-architecture.png" alt-text="Diagram showing the detailed Extended Events architecture.":::

  • Each Windows process can have one or more modules (Win32 process, Win32 module), also known as binaries or executable modules.
  • Each of the Windows process modules can contain one or more Extended Events packages (Package), which contain one or more Extended Events objects (Type, Target, Action, Map, Predicate, and Event).
  • Inside a host process, there can only be one instance of the Extended Events engine (Extended event engine), which:
    • Manages some aspects of the session (for example, enumerating sessions).
    • Handles dispatching (Dispatcher), similar to a thread pool.
    • Handles memory buffers (Buffer) for events. When buffers are filled, the buffers are dispatched to targets.
  • After a session is created and events are optionally bound to the session (Session context):
    • Instances of targets (Target instance) can also be created and added to the session.
    • When buffers are filled, those buffers are dispatched to targets.

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