SQL Server Reference Guide

Mar 28, 2003

␡

⎙ Print

< Back Page 200 of 365 Next >

There are actually multiple ways to evaluate the performance of a SQL Server system. I’ve explained how to examine the system from a holistic point of view — starting with the various components that make up the round-trip of data from the client through the network, the middle tiers (if any) and then on to the database system. Even within those components there are sub-components. For instance, within the client, middle-tier and database computers there is a CPU, a set of memory chips, network interfaces and storage units. In fact, even within those components are sub-components. Hard Drives have processors, small motherboard, memory caches and more.

I still advocate using that process to tune the system. While of course I’ll explain the specific steps around the SQL Server itself, it’s important to keep that holistic view in mind at all times.

Measuring Wait States

What I’ve explained to this point for performance tuning is the method of evaluating the components that are facing the most “pressure” on your database server — or the busiest components. But that’s actually only one way of considering the overall performance for the SQL Server part of the equation.

In this tutorial, I’ll introduce another method of evaluating where you should start your tuning efforts. This methodology doesn’t measure what is taking the most time in the system, it measures what the system is waiting on. And to do that, I’ll point you back to the “Dynamic Management Views” I explained in an earlier tutorial.

Along the way, I’ll use some of the other tools I’ve explained on this site — PowerShell and Excel. PowerShell, as I’ve explained in other articles, is a scripting environment built on the Dot-Net framework. And so is Microsoft Excel. I’ve explained how to use PowerShell to run a query against SQL Server, so in this tutorial I’ll combine all of those things to query SQL Server about its “Wait States” to find out what the system is waiting on. I’ll put that into an Excel spreadsheet so that you can visualize the data.

Wait States

Within SQL Server, there are various things that are happening at any one time. Microsoft has assigned various “categories” for these events, and called them “Wait States”. Each has a cause — some are internal, others are caused by query activity such as waiting on the logging events, locking and so on. Evaluating the wait states will tell you what to focus on. Reduce the wiats and you’lll speed up the system.

The Wait-State Query

So how do you find out what the system is waiting on? You can use a variety of tools, but the simplest is to query the sys.dm_os_wait_stats Dynamic Management View (DMV).

This view returns a lot of information, but I’m normally only after the top ten or so things that I should focus on, and normally I’m only interested in the ones that are taking the most time. You can query that DMV with a SELECT * (which will get everything), but this query, which I modified from one I found at this site, gives me the two columns I’m interested in – the wait type and the maximum time it has spent on my system. Try this on your test system:

SELECT TOP 10 
wait_type AS 'WaitType', max_wait_time_ms AS 'MaxWaitTime'
FROM    sys.dm_os_wait_stats
WHERE   wait_type NOT IN -- remove system waits   
('KSOURCE_WAKEUP', 'SLEEP_BPOOL_FLUSH', 'BROKER_TASK_STOP',
 'XE_TIMER_EVENT', 'XE_DISPATCHER_WAIT',
 'FT_IFTS_SCHEDULER_IDLE_WAIT', 'SQLTRACE_BUFFER_FLUSH',
 'CLR_AUTO_EVENT', 'BROKER_EVENTHANDLER', 'LAZYWRITER_SLEEP',
 'BAD_PAGE_PROCESS', 'BROKER_TRANSMITTER',
 'CHECKPOINT_QUEUE', 'DBMIRROR_EVENTS_QUEUE',
 'LAZYWRITER_SLEEP', 'ONDEMAND_TASK_QUEUE',
 'REQUEST_FOR_DEADLOCK_SEARCH', 'LOGMGR_QUEUE', 'SLEEP_TASK',
 'SQLTRACE_BUFFER_FLUSH', 'CLR_MANUAL_EVENT',
 'BROKER_RECEIVE_WAITFOR', 'PREEMPTIVE_OS_GETPROCADDRESS',
 'PREEMPTIVE_OS_AUTHENTICATIONOPS', 'BROKER_TO_FLUSH')
ORDER BY wait_time_ms DESC

That returns a fairly easy to read set of information, and on my system it returned the WRITELOG wait as the top item. I did a web search on that term, and I discovered that mean that the logging process was waiting, usually for the hard drive to respond. Sure enough, the hard drive where I had the log files was far too busy — I moved the files and things moved along faster.

The PowerShell Script

With that investigation complete, I decided to take that query and turn it into a PowerShell script. I’ve explained how to work with a PowerShell Query in another tutorial, so I’ll point you to that in the references below if you’re not familiar with it. Here’s the script, and you can see at the end that I’m storing the results in a variable called $Waits:

# Waits from SQL Server  to Excel Chart
# Keep this next part on one line... This gets your objects to put in the chart

$serverName = "UNIVAC"
$databaseName = "master"
$qry = @"
SELECT TOP 10 
wait_type AS 'WaitType', max_wait_time_ms AS 'MaxWaitTime'
FROM    sys.dm_os_wait_stats
WHERE   wait_type NOT IN -- remove system waits   
('KSOURCE_WAKEUP', 'SLEEP_BPOOL_FLUSH', 'BROKER_TASK_STOP',
 'XE_TIMER_EVENT', 'XE_DISPATCHER_WAIT',
 'FT_IFTS_SCHEDULER_IDLE_WAIT', 'SQLTRACE_BUFFER_FLUSH',
 'CLR_AUTO_EVENT', 'BROKER_EVENTHANDLER', 'LAZYWRITER_SLEEP',
 'BAD_PAGE_PROCESS', 'BROKER_TRANSMITTER',
 'CHECKPOINT_QUEUE', 'DBMIRROR_EVENTS_QUEUE',
 'LAZYWRITER_SLEEP', 'ONDEMAND_TASK_QUEUE',
 'REQUEST_FOR_DEADLOCK_SEARCH', 'LOGMGR_QUEUE', 'SLEEP_TASK',
 'SQLTRACE_BUFFER_FLUSH', 'CLR_MANUAL_EVENT',
 'BROKER_RECEIVE_WAITFOR', 'PREEMPTIVE_OS_GETPROCADDRESS',
 'PREEMPTIVE_OS_AUTHENTICATIONOPS', 'BROKER_TO_FLUSH')
ORDER BY wait_time_ms DESC
"@

function Get-SqlData {
param([string]$serverName=$(throw 'serverName is required.'), 
[string]$databaseName=$(throw 'databaseName is required.'),
[string]$query=$(throw 'query is required.'))     
Write-Verbose "Get-SqlData serverName:$serverName databaseName:$databaseName query:$query"
$connString = "Server=$serverName;Database=$databaseName;Integrated Security=SSPI;"
$da = New-Object "System.Data.SqlClient.SqlDataAdapter" ($query,$connString)    
$dt = New-Object "System.Data.DataTable"    
[void]$da.fill($dt)    
$dt 
} 
$Waits = Get-SqlData $serverName $databaseName $qry

Note that if you want to run this script on your system, you’ll need to change the server name to your Instance. Once you run it, you can just type $Waits to show the table returned.

Now all I need to do is create and Excel spreadsheet and then add a worksheet to it. From there, I’ll add the data from the table I returned from SQL Server. After that, I’ll take that data and add it to a chart in the Excel workbook. Here’s everything all put together:

$serverName = "UNIVAC"
$databaseName = "master"
$qry = @"
SELECT TOP 10 
wait_type AS 'WaitType', max_wait_time_ms AS 'MaxWaitTime'
FROM    sys.dm_os_wait_stats
WHERE   wait_type NOT IN -- remove system waits   
('KSOURCE_WAKEUP', 'SLEEP_BPOOL_FLUSH', 'BROKER_TASK_STOP',
 'XE_TIMER_EVENT', 'XE_DISPATCHER_WAIT',
 'FT_IFTS_SCHEDULER_IDLE_WAIT', 'SQLTRACE_BUFFER_FLUSH',
 'CLR_AUTO_EVENT', 'BROKER_EVENTHANDLER', 'LAZYWRITER_SLEEP',
 'BAD_PAGE_PROCESS', 'BROKER_TRANSMITTER',
 'CHECKPOINT_QUEUE', 'DBMIRROR_EVENTS_QUEUE',
 'LAZYWRITER_SLEEP', 'ONDEMAND_TASK_QUEUE',
 'REQUEST_FOR_DEADLOCK_SEARCH', 'LOGMGR_QUEUE', 'SLEEP_TASK',
 'SQLTRACE_BUFFER_FLUSH', 'CLR_MANUAL_EVENT',
 'BROKER_RECEIVE_WAITFOR', 'PREEMPTIVE_OS_GETPROCADDRESS',
 'PREEMPTIVE_OS_AUTHENTICATIONOPS', 'BROKER_TO_FLUSH')
ORDER BY wait_time_ms DESC
"@

function Get-SqlData {
param([string]$serverName=$(throw 'serverName is required.'), 
[string]$databaseName=$(throw 'databaseName is required.'),
[string]$query=$(throw 'query is required.'))     
Write-Verbose "Get-SqlData serverName:$serverName databaseName:$databaseName query:$query"
$connString = "Server=$serverName;Database=$databaseName;Integrated Security=SSPI;"
$da = New-Object "System.Data.SqlClient.SqlDataAdapter" ($query,$connString)    
$dt = New-Object "System.Data.DataTable"    
[void]$da.fill($dt)    
$dt 
} 
$Waits = Get-SqlData $serverName $databaseName $qry

$excel = new-object -comobject excel.application
$excel.visible = $true
$chartType = "microsoft.office.interop.excel.xlChartType.xlBarClustered" -as [type]
$workbook = $excel.workbooks.add()
$workbook.WorkSheets.item(1).Name = "Waits"
$sheet = $workbook.WorkSheets.Item("Waits")
$x = 2
$sheet.cells.item(1,1) = "Wait Type"
$sheet.cells.item(1,2) = "Max Wait Time"
Foreach($Wait in $Waits)
{
$sheet.cells.item($x,1) = $Wait.WaitType
$sheet.cells.item($x,2) = $Wait.MaxWaitTime
$x++
} 
$range = $sheet.usedRange
$range.EntireColumn.AutoFit()
$workbook.charts.add()
$workbook.ActiveChart.SetSourceData($range)

The Output

While the data is easy enough to look at, it really jumps out when you see it in a graph. Not only that, with the code stored in PowerShell, it can now be automated in multiple schedulers, including those in Windows or even in SQL Server 2008 SQL Agent Jobs.

Now I can track the wait states any time.

Figure 1

InformIT Articles and Sample Chapters

My Reference Guide series on working with PowerShell is here. The PowerShell script for running a query is here.

Books and eBooks

The “power” of PowerShell is in the fact it can work with SQL Server, the operating system, Excel and lots of other software. Learn more about that in Windows PowerShell Unleashed.

Online Resources

Want more PowerShell tips? Check out my MSDN series on that here.

< Back Page 200 of 365 Next >

🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Privacy Notice

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
Such marketing is consistent with applicable law and Pearson's legal obligations.
Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

As required by law.
With the consent of the individual (or their parent, if the individual is a minor)
In response to a subpoena, court order or legal process, to the extent permitted or required by law
To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
To investigate or address actual or suspected fraud or other illegal activities
To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020

Email Address