Paul White NZ (4/24/2010)
I believe Hugo is confusing the logging behaviour of TRUNCATE TABLE with the behaviour of minimally-logged data changes under the BULK_LOGGED recovery model.The allocation unit deallocations performed by TRUNCATE TABLE (whether or not these are deferred and performed asynchronously on a background thread) do not change data - so BCM bits are not set, and the affected pages are not included in the next log backup.
All that needs to be logged for full recoverability is the fact that the allocation units were deallocated. See Tracking Modified Extents for details of how SQL Server uses the Bulk Changed Map, and the impact on transaction log backups.
Yes, that was indeed what I was confused with. Thanks, Paul, for correcting me, and for providing the link to help me refresh my memory. All the bits and pieces were there, they just failed to connect in the right way 😀
And Tao, thank you for posting the script to demonstrate that I was wrong. Boy, if only I had taken the time to test this myself before posting... Ah well, water under the bridge.