MSSQL on Linux: Buffer Cache Hit Ratio

Microsoft.SQLServer.Linux.CollectionRule.DBEngine.BufferCacheHitRatio (Rule)

Collects the Linux "Buffer Cache Hit Ratio" performance counter for each instance of SQL DB Engine on Linux.

Knowledge Base article:

Summary

Percentage of pages found in the buffer cache without having to read from disk. The ratio is the total number of cache hits divided by the total number of cache lookups over the last few thousand page accesses. After a long period, the ratio moves very little. Because reading from the cache is much less expensive than reading from disk, you want this ratio to be high. Generally, you can increase the buffer cache hit ratio by increasing the amount of memory available to SQL Server.

Overridable Parameters

Name	Description	Default Value
Enabled	Enables or disables the workflow.	Yes
Interval (seconds)	The recurring interval of time in seconds in which to run the workflow.	900
Timeout (seconds)	Specifies the time the workflow is allowed to run before being closed and marked as failed.	300
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.Linux.DBEngine
Category	PerformanceCollection
Enabled	True
Alert Generate	False
Remotable	True

Member Modules:

ID	Module Type	TypeId	RunAs
DS	DataSource	Microsoft.SQLServer.Linux.DataSource.SqlOsPerformanceReader	Default
PerfMapper	ConditionDetection	System.Performance.DataGenericMapper	Default
WriteToDB	WriteAction	Microsoft.SystemCenter.CollectPerformanceData	Default
WriteToDW	WriteAction	Microsoft.SystemCenter.DataWarehouse.PublishPerformanceData	Default

Source Code:

<Rule ID="Microsoft.SQLServer.Linux.CollectionRule.DBEngine.BufferCacheHitRatio" Enabled="true" Target="SqlDiscL!Microsoft.SQLServer.Linux.DBEngine">

  <Category>PerformanceCollection</Category>

  <DataSources>

    <DataSource ID="DS" TypeID="Microsoft.SQLServer.Linux.DataSource.SqlOsPerformanceReader">

      <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>

      <SqlExecTimeoutSeconds>60</SqlExecTimeoutSeconds>

      <SqlTimeoutSeconds>15</SqlTimeoutSeconds>

      <TimeoutSeconds>300</TimeoutSeconds>

      <IntervalSeconds>900</IntervalSeconds>

      <ObjectName>$Target/Property[Type="SqlCoreLib!Microsoft.SQLServer.Core.DBEngine"]/PerformanceCounterObject$:Buffer Manager</ObjectName>

      <PerfInstanceName/>

      <PerfParams>

        <NameOfHandler>SqlOsPerfCounterReader</NameOfHandler>

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

        <CounterConfig>

          <CategoryName>Buffer Manager</CategoryName>

          <CounterName>Buffer cache hit ratio</CounterName>

          <BaseCounterName>Buffer cache hit ratio base</BaseCounterName>

          <InstanceSelector>2</InstanceSelector>

          <NeedsPrefix>1</NeedsPrefix>

          <InstanceIndex>0</InstanceIndex>

        </CounterConfig>

      </PerfParams>

    </DataSource>

  </DataSources>

  <ConditionDetection ID="PerfMapper" TypeID="SystemPerf!System.Performance.DataGenericMapper">

    <ObjectName>SQL DB Engine:Buffer Manager</ObjectName>

    <CounterName>Buffer cache hit ratio</CounterName>

    <InstanceName/>

    <Value>$Data/Property[@Name='CounterValue']$</Value>

  </ConditionDetection>

  <WriteActions>

    <WriteAction ID="WriteToDB" TypeID="SC!Microsoft.SystemCenter.CollectPerformanceData"/>

    <WriteAction ID="WriteToDW" TypeID="SCDW!Microsoft.SystemCenter.DataWarehouse.PublishPerformanceData"/>

  </WriteActions>

</Rule>