On the Debug -> System objects tab, you can see the numbers of objects currently stored in hash tables on the server.
The first table shows the names of particular hash tables and the numbers of records in them. The second table shows particular object types and the numbers of currently hashed objects of each type.
All hash tables can be cleared using the Clear hash tables button.
For more information about debugging in Kentico CMS, please refer to Developer's Guide -> Development -> Debugging and system information.