Ned Otter shows how to configure SQL Server to use memory-optimized metadata tables in TempDB:
Like other changes to TempDB, in order for the new memory-optimization to take effect a restart of the SQL Server service is required. Once the service is restarted, system tables in TempDB are now memory-optimized (it should be that way for RTM, but in CTP 3.0, it could be the case that not all system tables have been converted to Hekaton). You can reverse this setting with the following command, and again restarting the SQL Server service:
There are a couple of important notes that Ned gives us around accessing these metadata tables in scripts.