UpdateTraceW function (evntrace.h)

The UpdateTrace function updates the property setting of the specified event tracing session.

This function is obsolete. The ControlTrace function supersedes this function.


  TRACEHANDLE             TraceHandle,
  LPCWSTR                 InstanceName,



Handle to the event tracing session to be updated, or 0. You must specify a non-zero TraceHandle if InstanceName is NULL. This parameter will be used only if InstanceName is NULL. The handle is returned by the StartTrace.


Name of the event tracing session to be updated, or NULL. You must specify InstanceName if TraceHandle is 0.

To specify the NT Kernel Logger session, set InstanceName to KERNEL_LOGGER_NAME.


Pointer to an initialized EVENT_TRACE_PROPERTIES structure.

On input, the members must specify the new values for the properties to update. For information on which properties you can update, see Remarks.

On output, the structure members contains the updated settings and statistics for the event tracing session.

Return value

If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is one of the system error codes. The following table includes some common errors and their causes.


    The BufferSize member of the Wnode member of Properties specifies an incorrect size.


    One of the following is true:

    • Properties is NULL.
    • InstanceName and TraceHandle are both NULL.
    • InstanceName is NULL and TraceHandle is not a valid handle.
    • The LogFileNameOffset member of Properties is not valid.
    • The LoggerNameOffset member of Properties is not valid.

    Windows Server 2003 and Windows XP: The Guid member of the Wnode structure is SystemTraceControlGuid, but the InstanceName parameter is not KERNEL_LOGGER_NAME.


    Only users with administrative privileges, users in the Performance Log Users group, and services running as LocalSystem, LocalService, NetworkService can control event tracing sessions. To grant a restricted user the ability to control trace sessions, add them to the Performance Log Users group.

    Windows XP and Windows 2000: Anyone can control a trace session.


Event trace controllers call this function.

This function is obsolete. Instead, use ControlTrace with ControlCode set to EVENT_TRACE_CONTROL_UPDATE.

On input, the members must specify the new values for the properties to update. You can update the following properties.

  • EnableFlags: Set this member to 0 to disable all kernel providers. Otherwise, you must specify the kernel providers that you want to enable or keep enabled. Applies only to system logger sessions.

  • FlushTimer: Set this member if you want to change the time to wait before flushing buffers. If this member is 0, the member is not updated.

  • LogFileNameOffset: Set this member if you want to switch to another log file. If this member is 0, the file name is not updated. If the offset is not zero and you do not change the log file name, the function returns an error.

  • LogFileMode: Set this member if you want to turn EVENT_TRACE_REAL_TIME_MODE on and off. To turn real time consuming off, set this member to 0. To turn real time consuming on, set this member to EVENT_TRACE_REAL_TIME_MODE and it will be OR'd with the current modes.

  • MaximumBuffers: Set set this member if you want to change the maximum number of buffers that ETW uses. If this member is 0, the member is not updated.

For private logger sessions, you can only update LogFileNameOffset and FlushTimer.

If you are using a newly initialized EVENT_TRACE_PROPERTIES structure, the only members you need to specify, other than the members you are updating, are Wnode.BufferSize, Wnode.Guid, and Wnode.Flags.

If you use the property structure you passed to StartTrace, make sure the LogFileNameOffset member is 0 unless you are changing the log file name.

If you call the ControlTrace function to query the current session properties and then update those properties to update the session, make sure you set LogFileNameOffset to 0 (unless you are changing the log file name) and set EVENT_TRACE_PROPERTIES.Wnode.Flags to WNODE_FLAG_TRACED_GUID.

To obtain the property settings and session statistics for an event tracing session, call the ControlTrace function.


For an example that uses UpdateTrace, see Updating an Event Tracing Session.

[!NOTE] The evntrace.h header defines UpdateTrace as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.


Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header evntrace.h
Library Advapi32.lib
DLL Advapi32.dll

See also