Cant Reduce the Size of Temp DB in production , though the free space is 95%

Question

Hi,
In my production environment , the TempDb is consuming around 30 GB, where i can see the free space is around 95%.
I tried to shrink and end up with no results. I Canot go with Restarting the services, since its production server. So i have to ignore the same.
I even tried to clear cache, buffer by using below Queries.  but again didnt work out. 
DBCC FREEPROCCACHE -- clean cache
DBCC DROPCLEANBUFFERS -- clean buffers
DBCC FREESYSTEMCACHE ('ALL') -- clean system cache
DBCC FREESESSIONCACHE -- clean session cache
DBCC SHRINKDATABASE(tempdb, 10); -- shrink tempdb
dbcc shrinkfile ('tempdev') -- shrink db file
dbcc shrinkfile ('templog') -- shrink log file
I can see around few TempTables alive in tempdb, but those are very very small in size. I am not sure why this is not coming down. Can you please help me to suggest on the same. 
Thank you 
hemadri

Answer 1

Hi 
You need to identify what objects/data/plans consume disk space
-- Queries causing the most (de)allocations in tempDB
SELECT TOP 10
tsu.session_id, tsu.request_id, tsu.task_alloc, tsu.task_dealloc,
erq.command, erq.database_id, DB_NAME(erq.database_id) AS [database_name],
(SELECT SUBSTRING([text], statement_start_offset/2 + 1,
(CASE WHEN statement_end_offset = -1
THEN LEN(CONVERT(nvarchar(max), [text])) * 2
ELSE statement_end_offset
END - statement_start_offset) / 2
FROM sys.dm_exec_sql_text(erq.[sql_handle])) AS query_text,
qp.query_plan
FROM
(SELECT session_id, request_id, 
SUM(internal_objects_alloc_page_count + user_objects_alloc_page_count) as task_alloc,
SUM(internal_objects_dealloc_page_count + user_objects_dealloc_page_count) as task_dealloc
FROM sys.dm_db_task_space_usage
GROUP BY session_id, request_id) AS tsu
INNER JOIN sys.dm_exec_requests AS erq ON tsu.session_id = erq.session_id AND tsu.request_id = erq.request_id
OUTER APPLY sys.dm_exec_query_plan(erq.[plan_handle]) AS qp
WHERE tsu.session_id > 50 AND database_id >= 5
ORDER BY tsu.task_alloc DESC
GO
 ---to determine the space used by objects in TempDB:
SELECT
 SPID = s.session_id,
 s.[host_name],
 s.[program_name],
 s.status,
 r.granted_query_memory,
 t.text,
 sourcedb = DB_NAME(r.database_id),
 workdb = DB_NAME(dt.database_id),
 mg.*
FROM sys.dm_exec_sessions s
INNER JOIN sys.dm_exec_connections c
ON s.session_id = c.most_recent_session_id
LEFT OUTER JOIN sys.dm_exec_requests r
ON r.session_id = s.session_id
LEFT OUTER JOIN
  SELECT
   session_id,
   database_id
  FROM
   sys.dm_tran_session_transactions t WITH (NOLOCK)
  INNER JOIN
   sys.dm_tran_database_transactions dt WITH (NOLOCK)
  ON
   t.transaction_id = dt.transaction_id
 WHERE dt.database_id = DB_ID('tempdb')
GROUP BY
 session_id,
 database_id
) dt
ON s.session_id = dt.session_id
CROSS APPLY sys.dm_exec_sql_text(COALESCE(r.sql_handle, 
c.most_recent_sql_handle)) t
LEFT OUTER JOIN sys.dm_exec_query_memory_grants mg
ON s.session_id = mg.session_id
WHERE r.database_id = DB_ID('tempdb') OR dt.database_id = DB_ID('tempdb')
AND R.status = 'running';
Best Regards,Uri Dimant SQL Server MVP,
http://sqlblog.com/blogs/uri_dimant/
MS SQL optimization: MS SQL Development and Optimization
MS SQL Consulting:
Large scale of database and data cleansing
Remote DBA Services:
Improves MS SQL Database Performance
SQL Server Integration Services:
Business Intelligence