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Description:
This wait type is when a thread is waiting for an operation to do with the log pool. This is an in-memory cache of recently flushed log blocks, to help avoid log readers having to do physical reads of the log file (e.g. for sending log blocks to asynchronous availability group replicas).
(Books Online description: N/A)
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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 774 in 2012 and 792 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:
I have not seen this wait type be a noticeable contention point.
Known occurrences in SQL Server (list number matches call stack list):
- Waiting for access to a log consumer (in this case, while processing a notification from the memory manager)
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PostWait+9e
EventInternal<SuspendQueueSLock>::Wait+2ca
SOS_RWLock::GetLongWait+10b
LogConsumer::WaitOnConsumer+148
LogConsumer::NotifyConsumer+22
LogPoolMgr::NotifyLogPoolMgr+1e6
LogPool::Notify+20f
SOSHost_MemoryClerk::Notify+110
ResourceMonitor::NotifyMemoryConsumers+3dc
ResourceMonitor::ResourceMonitorTask+286
sqlservr.exe!SetupResourceMonitorTaskContext+105
SOS_Task::Param::Execute+21e
SOS_Scheduler::RunTask+a8