Thread Count

Microsoft.SQLServer.Windows.Monitor.DBEngine.ThreadCount (UnitMonitor)

Monitors free thread count for Microsoft SQL Server instance on Windows.

Knowledge Base article:

Summary

Usually, SQL Server opens a system thread for each query request but if the amount of threads exceeds the specified max worker threads value, SQL Server pools the worker threads. When all worker threads are active with long running queries, SQL Server may appear unresponsive until a worker thread completes and becomes available. Though not a defect, this can sometimes be undesirable. The monitor analyzes the number of free threads in the VISIBLE ONLINE scheduler status and notifies if the amount is low.

Causes

An increase in the amount of work causes an increase in utilized threads. This could indicate that SQL Server is working under a significant load or an excessive number of queries are running in parallel.

Resolutions

Adjusting max worker threads is an advanced option and should be changed only by experienced database administrators or certified SQL Server technicians.

Thread pooling helps optimize performance when large numbers of clients are connected to the server. Usually, a separate operating system thread is created for each query request. However, with hundreds of connections to the server, using one thread per query request can consume large amounts of system resources. The max worker threads option enables SQL Server to create a pool of worker threads to service a larger number of query requests, which improves performance.

External

Configure the max worker threads Server Configuration Option

Overridable Parameters

Name	Description	Default Value
Alert Priority	Defines Alert Priority.	Normal
Alert Severity	Defines Alert Severity.	Error
Enabled	Enables or disables the workflow.	Yes
Generates Alerts	Defines whether the workflow generates an Alert.	Yes
Interval (seconds)	The recurring interval of time in seconds in which to run the workflow.	300
Minimum Free Threads Threshold	The workflow determines the maximum number of threads and the number of active threads for each DB Engine process. An alert will be generated if the number of free threads is less or equal than this parameter.	10
Number of samples	Indicates how many times a measured value should breach a threshold before the state is changed.	6
Synchronization Time	The synchronization time is specified by using a 24-hour format. Can be omitted.
Timeout (seconds)	Specifies the time the workflow is allowed to run before being closed and marked as failed.	200
Timeout for query execution (seconds)	The workflow will fail and register an event, if the query execution takes longer than the specified period.	60
Timeout for database connection (seconds)	The workflow will fail and register an event, if it cannot access the database during the specified period.	15

Element properties:

Target

Microsoft.SQLServer.Windows.DBEngine

Parent Monitor

System.Health.PerformanceState

Category

PerformanceHealth

Enabled

True

Alert Generate

True

Alert Severity

Error

Alert Priority

Normal

Alert Auto Resolve

True

Monitor Type

Microsoft.SQLServer.Windows.MonitorType.DBEngine.ThreadCount

Remotable

True

Accessibility

Public

Alert Message

MSSQL on Windows: Free thread count is too low

Free thread count on SQL Server instance "{1}", computer "{0}" is too low. See the "Alert Context" tab for more details.

RunAs

Default

Source Code:

<UnitMonitor ID="Microsoft.SQLServer.Windows.Monitor.DBEngine.ThreadCount" Accessibility="Public" Enabled="true" Target="SqlDiscW!Microsoft.SQLServer.Windows.DBEngine" ParentMonitorID="Health!System.Health.PerformanceState" Remotable="true" Priority="Normal" TypeID="Microsoft.SQLServer.Windows.MonitorType.DBEngine.ThreadCount" ConfirmDelivery="false">

  <Category>PerformanceHealth</Category>

  <AlertSettings AlertMessage="Microsoft.SQLServer.Windows.Monitor.DBEngine.ThreadCount.AlertMessage">

    <AlertOnState>Error</AlertOnState>

    <AutoResolve>true</AutoResolve>

    <AlertPriority>Normal</AlertPriority>

    <AlertSeverity>Error</AlertSeverity>

    <AlertParameters>

      <AlertParameter1>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/MachineName$</AlertParameter1>

      <AlertParameter2>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/InstanceName$</AlertParameter2>

    </AlertParameters>

  </AlertSettings>

  <OperationalStates>

    <OperationalState ID="Normal" MonitorTypeStateID="Normal" HealthState="Success"/>

    <OperationalState ID="Error" MonitorTypeStateID="Error" HealthState="Error"/>

  </OperationalStates>

  <Configuration>

    <MachineName>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/MachineName$</MachineName>

    <NetbiosComputerName>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/NetbiosComputerName$</NetbiosComputerName>

    <InstanceName>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/InstanceName$</InstanceName>

    <ConnectionString>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/ConnectionString$</ConnectionString>

    <InstanceVersion>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/Version$</InstanceVersion>

    <InstanceEdition>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/Edition$</InstanceEdition>

    <MonitoringType>$Target/Property[Type="SqlDiscW!Microsoft.SQLServer.Windows.DBEngine"]/MonitoringType$</MonitoringType>

    <IntervalSeconds>300</IntervalSeconds>

    <SyncTime/>

    <MinFreeThreadsCount>10</MinFreeThreadsCount>

    <NumSamples>6</NumSamples>

    <TimeoutSeconds>200</TimeoutSeconds>

    <SqlExecTimeoutSeconds>60</SqlExecTimeoutSeconds>

    <SqlTimeoutSeconds>15</SqlTimeoutSeconds>

  </Configuration>

</UnitMonitor>