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Event File Target

The event file target is a target that writes complete buffers to disk.

The following table describes the available options for configuring the event file target.

Option

Allowed values

Description

filename

Any string up to 260 characters. This value is required.

The file location and filename.

You can use any filename extension.

max_file_size

Any 64 bit integer. This value is optional.

The maximum file size in megabytes (MB). If max_file_size is not specified, the file will grow until the disk is full. The default file size is 1GB.

max_file_size must be larger than the current size of the session buffers. If it is not, the file target will fail to initialize, reporting that the max_file_size is invalid. To view the current size of the buffers, query the buffer_size column in the sys.dm_xe_sessions dynamic management view.

If the default file size is smaller than the session buffer size, we recommend setting max_file_size to the value specified in the max_memory column in the sys.server_event_sessions catalog view.

When max_file_size is set to a size larger than the size of the session buffers, it may be rounded down to the nearest multiple of the session buffer size. This may create a target file that is smaller than the specified value of max_file_size. For example, if the buffer size is 100MB and max_file_size is set to 150MB, the resultant file size is rounded down to 100MB because a second buffer would not fit in the remaining 50MB of space.

If the default file size is smaller than the session buffer size, we recommend setting max_file_size to the value in the max_memory column in the sys.server_event_sessions catalog view.

max_rollover_files

Any 32 bit integer. This value is optional.

The maximum number of files to retain in the file system.

increment

Any 32 bit integer. This value is optional.

The incremental growth, in megabytes (MB), for the file. If unspecified, the default value for increment is twice the session buffer size.

The first time that an event file target is created, the filename you specify is appended with _0_ and a long integer value. The integer value is calculated as the number of milliseconds between January 1, 1600 and the date and time the file is created. Subsequent rollover files also use this format. From examining the value of the long integer, you can determine the most current file. The following example illustrates how files are named in a scenario where you specify the filename option as C:\OutputFiles\MyOutput.xel:

  • first file created - C:\OutputFiles\MyOutput_0_128500310259380000.xel

  • first rollover file - C:\OutputFiles\MyOutput_0_128505831770890000.xel

  • second rollover file - C:\OutputFiles\MyOutput_0_132410772966237000.xel

To add the event file target to an Extended Events session, you would include the following statements when you create or alter an event session, replacing file_name with the desired file name and path:

ADD TARGET package0.event_file(
   SET filename='file_name.xel')

To review the output from the file target, you must use the sys.fn_xe_file_target_read_file function. We recommend that you cast the data as XML. You can use the following syntax, replacing file_name with the file name and path that you specified when you added the target:

SELECT *, CAST(event_data AS XML) AS 'event_data_XML'
FROM sys.fn_xe_file_target_read_file('file_name*.xel', NULL, NULL, NULL)
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