I have no answer, but there are ways to find out more.
, , . proc , SQL Server .
NotificationJob.Destination, QueuedDt CompletedDt, not exists . concurrency.
, proc, . , 1200, proc, . , proc. , .
dbcc traceon (1200, -1) -- print detailed information for every lock request. DO NOT DO THIS ON A PRODUCTION SYSTEM!
exec dbo.Notification_DequeueJob
dbcc traceoff (1200, -1) -- turn off the trace flag ASAP
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