CXSYNC_PORT

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Description:

The simplest explanation of this wait type is that there are parallel plans running. This wait type was added in Azure SQL Database and Azure SQL Managed Instance and is now in SQL Server 2022. This, along with CXSYNC_CONSUMER, were split out from CXPACKET in a bid to make investigating parallel plan performance issues easier.

I do not have any experience with this wait yet.

Do not just reduce the server MAXDOP to try to reduce or remove these! See CXPACKET for more information.

(Books Online description: “Occurs with parallel query plans when waiting to open, close, and synchronize Exchange Iterator ports between producer and consumer threads. For example, if a query plan has a long sort operation, CXSYNC_PORT waits may be higher because the sort must complete before the Exchange Iterator port can be synchronized.”)

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Added in SQL Server version:

Azure SQL Database, Azure SQL Managed Instance, SQL Server 2022.

Removed in SQL Server version:

N/A

Extended Events wait_type value:

TBD

Other information:

TBD

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

1. Exchanging information during a sort operation
2. Exchanging information as part of a stream aggregate during a statistics update

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

1. SOS_Task::PostWait
   WaitableBase::Wait
   SOS_WaitableAddress::WaitAllowPrematureWakeup
   XchngWait<XPortSLock>
   CXPort::Open
   CQScanExchangeNew::Open
   CQScanNew::OpenHelper
   CQScanNew::OpenHelper
   CQScanSortNew::BuildSortTable
   CQScanSortNew::OpenHelper
   CQScanNew::OpenHelper
   CQScanStreamAggregateNew::Open
   CQScanNew::OpenHelper
   CQScanXProducerNew::Open
   FnProducerOpen
   FnProducerThread
   SubprocEntrypoint
   SOS_Task::Param::Execute
   SOS_Scheduler::RunTask
2. SOS_Task::PostWait
   WaitableBase::Wait
   SOS_WaitableAddress::WaitAllowPrematureWakeup
   XchngWait<XPortSLock>
   CXPort::Open
   CQScanExchangeNew::Open
   CQScanNew::OpenHelper
   CQScanStreamAggregateNew::Open
   CQueryScan::StartupQuery
   CXStmtQuery::SetupQueryScanAndExpression
   CXStmtQuery::InitForExecute
   CXStmtQuery::ErsqExecuteQuery
   CXStmtSelect::XretExecute
   CExecStmtLoopVars::ExecuteXStmtAndSetXretReturn
   CMsqlExecContext::ExecuteStmts<1,1>
   CMsqlExecContext::FExecute
   CSQLSource::Execute
   CStatsUtil::ExecInternalStatsQuery
   CStatsUtil::PCStatManMaxdiffHistogram
   CStatsUtil::PersistQPStatsInCatalogs
   CStatsUtil::FUpdateQPStatsHelper
   CQPJobStatsUpdate::Invoke
   CQPJob::FDoQPJob
   CQPOnDemandTask::ExecuteQPJob
   PeriodicTimerTask::ProcessTskPkt
   TaskReqPktTimer::ExecuteTask
   OnDemandTaskContext::ProcessTskPkt
   SystemTaskEntryPoint
   OnDemandTaskContext::FuncEntryPoint
   SOS_Task::Param::Execute
   SOS_Scheduler::RunTask