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This wait was added in various versions as part of a bug fix, and then removed again in the very next CU for each of those versions because the bug fix was flawed. Paul White has a great write-up on the bug and circumstances around it here.
(Books Online description: N/A)
Questions/comments on this wait type? Click here to send Paul an email, especially if you have any information to add to this topic.
Added in SQL Server version:
Removed in SQL Server version:
Next CUs after it was added.