when i run the DBCC SHRINKFILE i get this error message

DBCC SHRINKFILE: Page 1:3740312 could not be moved because it is a work table page.

but the free space on the tempdb is 29GB.

how can i know what i keeping my tempdb busy,so i can't shrink it?

sp_spaceused =

database_name database_size unallocated space

-------------------------------------------------------------------------------------------------------------------------------- ------------------ ------------------

tempdb 29971.25 MB 29219.73 MB

reserved data index_size unused

------------------ ------------------ ------------------ ------------------

1560 KB 648 KB 712 KB 200 KB