select log_reuse_wait_desc from sys.databases where name = 'tempdb'

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SELECT SUM(unallocated_extent_page_count) AS [free pages],
    (SUM(unallocated_extent_page_count)*1.0/128) AS [free space in MB],
    SUM(internal_object_reserved_page_count) AS [internal object pages used],
    (SUM(internal_object_reserved_page_count)*1.0/128) AS [internal object space in MB],
    SUM(user_object_reserved_page_count) AS [user object pages used],
    (SUM(user_object_reserved_page_count)*1.0/128) AS [user object space in MB]
FROM sys.dm_db_file_space_usage;

SELECT SUM(size)*1.0/128 AS [size in MB]
FROM tempdb.sys.database_files

free pages   free space in MB  internal object pages used internal object space in MB  user object pages used user object space in MB
------------ ----------------- -------------------------- ---------------------------- ---------------------- -----------------------
1829424      14292.375000      320                        2.500000                     80                     0.625000

size in MB
-------------
22490.062500

SELECT t1.name AS [Service_Name],  t3.name AS [Schema_Name], t2.name AS [Queue_Name],
    CASE WHEN t4.state IS NULL THEN 'Not available'
        ELSE t4.state
        END AS [Queue_State],
    CASE WHEN t4.tasks_waiting IS NULL THEN '--'
        ELSE CONVERT(VARCHAR, t4.tasks_waiting)
        END AS tasks_waiting,
    CASE WHEN t4.last_activated_time IS NULL THEN '--'
        ELSE CONVERT(varchar, t4.last_activated_time)
        END AS last_activated_time ,
    CASE WHEN t4.last_empty_rowset_time IS NULL THEN '--'
        ELSE CONVERT(varchar,t4.last_empty_rowset_time)
        END AS last_empty_rowset_time,
(
    SELECT COUNT(*)
    FROM sys.transmission_queue t6
    WHERE (t6.from_service_name = t1.name)
) AS [Tran_Message_Count]
FROM sys.services t1
INNER JOIN sys.service_queues t2
    ON ( t1.service_queue_id = t2.object_id )
INNER JOIN sys.schemas t3
    ON ( t2.schema_id = t3.schema_id )
LEFT OUTER JOIN sys.dm_broker_queue_monitors t4
    ON ( t2.object_id = t4.queue_id  AND t4.database_id = DB_ID() )
INNER JOIN sys.databases t5
    ON ( t5.database_id = DB_ID() )

Service_Name                                                              Schema_Name  Queue_Name                    Queue_State     tasks_waiting  last_activated_time  last_empty_rowset_time  Tran_Message_Count
------------------------------------------------------------------------- ------------ ----------------------------- --------------- -------------- -------------------- ----------------------- -------------------
InternalMailService                                                       dbo          InternalMailQueue             INACTIVE        0              Apr  7 2013  8:10AM  Apr  7 2013  8:10AM     0
ExternalMailService                                                       dbo          ExternalMailQueue             INACTIVE        0              Apr  7 2013  8:10AM  Apr  7 2013  8:10AM     0
http://schemas.microsoft.com/SQL/Notifications/QueryNotificationService   dbo          QueryNotificationErrorsQueue  Not available   --             --                   --                      0
http://schemas.microsoft.com/SQL/Notifications/EventNotificationService   dbo          EventNotificationErrorsQueue  Not available   --             --                   --                      0
http://schemas.microsoft.com/SQL/ServiceBroker/ServiceBroker              dbo          ServiceBrokerQueue            Not available   --             --                   --                      0

SELECT OBJECT_NAME(id), rowcnt
    FROM tempdb..sysindexes
    WHERE OBJECT_NAME(id) LIKE '#%'
    ORDER BY rowcnt DESC


SELECT
SUM (user_object_reserved_page_count)*8 as usr_obj_kb,
SUM (internal_object_reserved_page_count)*8 as internal_obj_kb,
SUM (version_store_reserved_page_count)*8 as version_store_kb,
SUM (unallocated_extent_page_count)*8 as freespace_kb,
SUM (mixed_extent_page_count)*8 as mixedextent_kb,
SUM (User_object_reserved_page_count +
internal_object_reserved_page_count +
version_store_reserved_page_count +
unallocated_extent_page_count +
mixed_extent_page_count) * 8 as total_space
FROM sys.dm_db_file_space_usage

USE [tempdb]
GO
DBCC FREEPROCCACHE  -- this will free up all cache plans
GO
USE [tempdb]
GO
DBCC SHRINKFILE (N'tempdev' , 10000) -- will shrink the mdf file to 10GB, you can specify log file as well
GO