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Description:
This wait type seems to be when a thread needs to allocate memory and there is none available. It waits for a small amount of time, assuming that something else in the system will create some free memory for it to allocate.
(Books Online description: N/A)
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Added in SQL Server version:
2016
Removed in SQL Server version:
N/A
Extended Events wait_type value:
The map_key value in sys.dm_xe_map_values is 1096 in 2016 RTM. After 2016 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, but if they start to increase on your system, that’s a sign that the instance is under memory pressure, which may indicate other problems on the instance.
Known occurrences in SQL Server (list number matches call stack list):
- Waiting for memory to become available, in this case while allocating memory for the internals of a stream aggregate
And many other similar call stacks.
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PostWait+0x6f
SOS_Task::Sleep+0x12f
SOS_BackOff+0x169
SOS_MemoryPool::AllocatePages+0x21b
MemoryPoolManager::AllocatePages+0x193
MemoryNode::AllocatePagesInternal+0x290
MemoryClerkInternal::AllocatePagesWithFailureMode+0x176
MemoryClerkInternal::AllocatePages+0x3d
CIncPageMgr::PbAllocateWithNewPage+0x83
CMemProc::Alloc+0x88
operator new[]+0x4a
CQScanSeqProjectNew::CQScanSeqProjectNew+0x270
CXteSeqProject::QScanGet+0x94
CQScanSortNew::CQScanSortNew+0xcc
CQScanXSortNew::CQScanXSortNew+0x28
CXteSort::QScanGet+0x244
CQScanStreamAggregateNew::CQScanStreamAggregateNew+0xf5
CXteStreamAggregate::QScanGet+0xf8
CBpXte::PqsInitializeBatchProcessingTree+0x4e
CQScanXProducerNew::CQScanXProducerNew+0x1a6
FnProducerThread+0x669
SubprocEntrypoint+0xd25