DMV to track the temp file usage for SQLServer

There are
three DMVs you can use to track tempdb usage:

sys.dm_db_task_space_usage
sys.dm_db_session_space_usage
sys.dm_db_file_space_usage

The
first two will allow you to track allocations at a query & session
level. The third tracks allocations across version store, user and internal
objects.

The
following example query will give you allocations per session:

SELECT
s.session_id
AS [SESSION ID]
,DB_NAME(database_id)
AS [DATABASE Name]
,HOST_NAME
AS [System Name]
,program_name
AS [Program Name]
,login_name
AS [USER Name]
,status
,cpu_time
AS [CPU TIME (in milisec)]
,total_scheduled_time
AS [Total Scheduled TIME (in milisec)]
,total_elapsed_time
AS [Elapsed TIME (in milisec)]
,(memory_usage
* 8) AS [Memory USAGE (in KB)]
,(user_objects_alloc_page_count
* 8) AS [SPACE Allocated FOR USER Objects (in KB)]
,(user_objects_dealloc_page_count
* 8) AS [SPACE Deallocated FOR USER Objects (in KB)]
,(internal_objects_alloc_page_count
* 8) AS [SPACE Allocated FOR Internal Objects (in KB)]
,(internal_objects_dealloc_page_count
* 8) AS [SPACE Deallocated FOR Internal Objects (in KB)]
,CASE
is_user_process
WHEN
1 THEN ‘user session‘
WHEN
0 THEN ‘system session‘
END
AS [SESSION Type],
s.row_count
AS [ROW COUNT]
FROM
sys.dm_db_session_space_usage su INNER join sys.dm_exec_sessions s ON
su.session_id = s.session_id

Below are the
situation when SQL Server will use the temp file.

1. usage
   of table variables or temporary tables


2. sql
   server created intermediate resultsets as worktables in tempdb - usually for
   sorting purposes (usually is a sign of absent indexes/out-of-date
   statistics)


3. sql
   server decided to pre-evaluate the resultset of table valued function and in
   this case it stores the data in tempdb


4. recreating
   indexes with option SORT_IN_TEMPDB = ON