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PREEMPTIVE_HADR_LEASE_MECHANISM

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Description:

This wait type is when a thread switches to preemptive mode as part of renewing the lease between the failover cluster and the SQL Server resource DLL because of a lease timeout. The lease is essentially a health check mechanism, and a timeout indicates there is a problem with the availability group.

(Books Online description: “Always On Availability Groups lease manager scheduling for CSS diagnostics.”)

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Added in SQL Server version:

2012

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 862 in 2012 and 881 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

Here are some links to help with troubleshooting the problems that could cause a lease timeout, leading to this wait type occurring:

Anecdotal evidence indicates that network problems seem to be the major cause of lease timeouts.

Known occurrences in SQL Server (list number matches call stack list):

  1. TBD

Abbreviated call stacks (list number matches known occurrences list):

  1. TBD