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sys.database_event_sessions (Azure SQL Database and Azure SQL Managed Instance)

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Applies to: Azure SQL Database Azure SQL Managed Instance

Lists all the database-scoped event session definitions that exist in the current database. For information about active database-scoped event sessions, see sys.dm_xe_database_sessions.

Azure SQL Database supports only database-scoped sessions. Azure SQL Managed Instance supports both database-scoped sessions and server-scoped sessions. Server-scoped sessions are recommended for managed instances: learn more in CREATE EVENT SESSION.

Column name Data type Description
event_session_id int The unique ID of the event session. Is not nullable.
name sysname The user-defined name for identifying the event session. name is unique. Is not nullable.
event_retention_mode nchar(1) Determines how event loss is handled. The default is S. Is not nullable. Is one of:

S. Maps to event_retention_mode_desc = ALLOW_SINGLE_EVENT_LOSS

M. Maps to event_retention_mode_desc = ALLOW_MULTIPLE_EVENT_LOSS

N. Maps to event_retention_mode_desc = NO_EVENT_LOSS
event_retention_mode_desc sysname Describes how event loss is handled. The default is ALLOW_SINGLE_EVENT_LOSS. Is not nullable. Is one of:

ALLOW_SINGLE_EVENT_LOSS. Events can be lost from the session. Single events are dropped only when all event buffers are full. Losing single events when buffers are full allows for acceptable SQL Server performance characteristics, while minimizing the loss in the processed event stream.

ALLOW_MULTIPLE_EVENT_LOSS. Full event buffers can be lost from the session. The number of events lost depends on the memory size allocated to the session, the partitioning of the memory, and the size of the events in the buffer. This option minimizes performance impact on the server when event buffers are quickly filled. However, large numbers of events can be lost from the session.

NO_EVENT_LOSS. No event loss is allowed. This option ensures that all events raised are retained. Using this option forces all the tasks that fire events to wait until space is available in an event buffer. This may lead to detectable performance degradation while the event session is active. For event file targets in Azure SQL Database, behaves the same as ALLOW_SINGLE_EVENT_LOSS. For more information, see EVENT_RETENTION_MODE.
max_dispatch_latency int The amount of time, in milliseconds, that events are buffered in memory before they're served to session targets. Valid values are from 1 to 2147483648, and -1. A value of -1 indicates that dispatch latency is infinite. Is nullable.
max_memory int The amount of memory allocated to the session for event buffering. The default value is 4 MB. Is nullable.
max_event_size int The amount of memory set aside for events that don't fit in event session buffers. If max_event_size exceeds the calculated buffer size, two additional buffers of max_event_size are allocated to the event session. Is nullable.
memory_partition_mode nchar(1) The location in memory where event buffers are created. The default partition mode is G. Is not nullable. memory_partition_mode is one of:

G - NONE

C - PER_CPU

N - PER_NODE
memory_partition_mode_desc sysname The default is NONE. Is not nullable. Is one of:

NONE. A single set of buffers are created within a SQL Server instance.

PER_CPU. A set of buffers is created for each CPU.

PER_NODE. A set of buffers is created for each non-uniform memory access (NUMA) node.
track_causality bit Enable or disable causality tracking. If set to 1 (ON), tracking is enabled and related events on different server connections can be correlated. The default setting is 0 (OFF). Is not nullable.
startup_state bit Value determines whether or not session is started automatically when the server starts. The default is 0. Is not nullable. Is one of:

0 (OFF). The session doesn't start when the server starts.

1 (ON). The event session starts when the server starts.

Permissions

Requires the VIEW DATABASE STATE permission.

Next steps

Learn more about related concepts in the following articles: