thanks for the reply guys. I have a strong feeling it might be down to a few crashes and restore of the database we had in between this issue, we have made a few changes to assign more memory resource to the database so we are monitoring this and also we think next step is to place the temp database on its own drive.

The crashes we were having were due to the server crashing and corrupting the database as Applications are constantly writing to it, we would then have to restore via a TSM backup because the database would restart in a emergency mode.