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Posted Oct 30, 2007

How to Build a Profile Script to Monitor SQL Server off Hours

By Gregory A. Larsen

SQL Server Profiler is a valuable tool for monitoring activity against your SQL Server environment. With this tool, you can monitor numerous events depending on what kind of performance problem you are trying to track down. This tool is normally used in real time, where the events being monitored are displayed on your computer monitor. However, displaying the information in real time doesn’t always work for every situation you might be monitoring. What if you have a performance problem that routinely occurs in the middle of the night, when you are normally sleeping? I’m sure most DBAs would rather sleep, than stay at work so they could monitor a performance problem in the middle of the night. Well don’t lose any sleep, read the rest of this article and find out how to build a Profiler script that can be run off hours.

Scripting a Profiler Trace

There are two key pieces to running Profiler traces at night. The first one is to be able to script a Profiler trace definition. The second important piece is to output the events being traced to some place other than a computer monitor. Let’s look at how you can script a trace and log the output to a location other than the screen.

There are two methods to script a Profiler trace. The first method is to dig into Books Online and determine all the stored procedures (SPs) necessary to identify all the events you want to trace and how to start/stop your trace; but this would be the hard way to go about scripting a trace. Microsoft has made it easy to script a Profiler trace, by providing a scripting option built into the GUI Profiler tool.

Microsoft has provided two different options for saving Profiler trace output. Output can go to a log file or a SQL Server table. The performance overhead of saving your trace to a file is much less than saving trace output to a SQL Server table. The advantage of saving trace information to a table is you can then use T-SQL commands to analyze your trace data. You need to decide which output format works for you.

Before I can demo how to use Profiler to create a Profiler script I need to determine what trace events I want to capture. For the purposes of my demo below, I’m only going to log the start and stop events for T-SQL statements and the executions of SPs. As stated above I am going to use the Profiler GUI to create my Profile trace script. To start Profiler I click on the “Start” button, place my mouse on the “All Programs” item, then hover the mouse over the “SQL Server 2005” item, in the drop down I hover over the “Performance tools” icon, and finally click on the “SQL Server Profiler” item. When I do this, the following window is displayed:

To build my trace definition and create my Profiler trace script, I click on the “File” menu item, select the “New Trace” item and then connect to the SQL Server I want to monitor. Doing this will bring up the following screen:

On this screen, I can identify the name of my trace, the template I want to use, where I want to save the trace output, and time I want my trace to stop. For my demo I will be creating a trace that is named “AdventureWorks Performance problem”, which saves the Profiler trace events to file named “c:\temp\AW_problem.trc”. Once I fill out the above screen to meet this requirement my screen will look like this:

Note that I have not checked the “Server processes trace data” option. When this option is checked, SQL Server will make sure every event is written to your trace file, even if it degrades performance. I also enabled the trace to stop but left the default stop time. Which you can see the stop time is not in the middle of the night. I will discuss setting the appropriate stop time option later on in this article.

If I wanted to save my trace to a SQL Server database, instead of a file I would use the “Save to table” checkbox. Below is a screenshot of where I identified my output to go to a table, instead of a log file:

Here I have identified that my trace output would be saved to the PerformanceProblem table in the AdventureWorks database. I could use either one of these options to capture my trace information. The save to a file option incurs less overhead, so I normally use that method. For my demo below, I will be using the saved to a file option.

Now that I’ve identified the output of the Profiler events, I need to identify the events I want to monitor. I do that by using the “Event Selection” tab on the “Trace Properties” window. Here is a screen shot of the events I selected:

All I wanted to capture for my trace is the SP and the Statement starts and stops events. Then for each of these events I captured the TextData column so I would able to determine what batch or statement is being executed. For each SP or statement, I wanted to know the CPU, Read, Write, and Duration information, so I can determine the amount of resources each batch or statement consumed. I use the StartTime and EndTime to help me know the actual time frames each SP and statement was executed. Lastly, I wanted to know the DatabaseName so I know which database to associate each SP or statement event. Note that if an application uses fully qualified names in their queries then the DatabaseName might be misleading, because it contains the name of the database from which the SP or statement was executed, not the database in which the SP or statement processes against. I could have filtered my Profiler trace down to a single database, but remember I’m setting up a trace definition to resolve a performance problem off hours. If the performance problem is associated with another application running that is consuming resources at the same time as my poorly performing application this would be valuable information to know. This is why initially I am not going to filter my trace to just log events from the AdventureWorks database.

My goal of going through the Profile GUI is not to start a trace, but to generate the Profiler script of the trace definition I just specified that I would need to start my trace. After my trace is started, I will immediately stop the trace and create the script. So, on the above screen I will click on the “Run” button. This will bring up the following screen:

As I already stated I will stop my trace as soon as it starts. To stop my trace I can either click on the red square icon on the toolbar, or go to the “File” menu and then selecting the “Stop Trace” option.

Once my trace is stopped, I can create my Profile trace definition by using the “Export” function. In the screenshot below you can see how I used the File menu item, to navigate to the “Export” item, then selected the “Script Trace Definition”, so I can create my Profiler trace script:

After I click on the “For SQL Server 2005…” items, I am prompted for a place to store my T-SQL script for this trace. For my particular trace above, the following script was generated. You need to look closely at this script, because a few things will need to be changed before I run it off hours:

/****************************************************/
/* Created by: SQL Server Profiler 2005             */
/* Date: 10/17/2007  05:46:05 PM         */
/****************************************************/


-- Create a Queue
declare @rc int
declare @TraceID int
declare @maxfilesize bigint
declare @DateTime datetime

set @DateTime = '2007-10-17 18:32:58.000'
set @maxfilesize = 5 

-- Please replace the text InsertFileNameHere, with an appropriate
-- filename prefixed by a path, e.g., c:\MyFolder\MyTrace. The .trc extension
-- will be appended to the filename automatically. If you are writing from
-- remote server to local drive, please use UNC path and make sure server has
-- write access to your network share

exec @rc = sp_trace_create @TraceID output, 0, N'InsertFileNameHere', @maxfilesize, @Datetime
if (@rc != 0) goto error

-- Client side File and Table cannot be scripted

-- Set the events
declare @on bit
set @on = 1
exec sp_trace_setevent @TraceID, 45, 16, @on
exec sp_trace_setevent @TraceID, 45, 1, @on
exec sp_trace_setevent @TraceID, 45, 9, @on
exec sp_trace_setevent @TraceID, 45, 17, @on
exec sp_trace_setevent @TraceID, 45, 18, @on
exec sp_trace_setevent @TraceID, 45, 35, @on
exec sp_trace_setevent @TraceID, 45, 12, @on
exec sp_trace_setevent @TraceID, 45, 13, @on
exec sp_trace_setevent @TraceID, 45, 14, @on
exec sp_trace_setevent @TraceID, 45, 15, @on
exec sp_trace_setevent @TraceID, 44, 1, @on
exec sp_trace_setevent @TraceID, 44, 9, @on
exec sp_trace_setevent @TraceID, 44, 35, @on
exec sp_trace_setevent @TraceID, 44, 12, @on
exec sp_trace_setevent @TraceID, 44, 14, @on
exec sp_trace_setevent @TraceID, 41, 15, @on
exec sp_trace_setevent @TraceID, 41, 16, @on
exec sp_trace_setevent @TraceID, 41, 1, @on
exec sp_trace_setevent @TraceID, 41, 9, @on
exec sp_trace_setevent @TraceID, 41, 17, @on
exec sp_trace_setevent @TraceID, 41, 18, @on
exec sp_trace_setevent @TraceID, 41, 35, @on
exec sp_trace_setevent @TraceID, 41, 12, @on
exec sp_trace_setevent @TraceID, 41, 13, @on
exec sp_trace_setevent @TraceID, 41, 14, @on
exec sp_trace_setevent @TraceID, 166, 1, @on
exec sp_trace_setevent @TraceID, 166, 9, @on
exec sp_trace_setevent @TraceID, 166, 35, @on
exec sp_trace_setevent @TraceID, 166, 12, @on
exec sp_trace_setevent @TraceID, 166, 14, @on


-- Set the Filters
declare @intfilter int
declare @bigintfilter bigint

-- Set the trace status to start
exec sp_trace_setstatus @TraceID, 1

-- display trace id for future references
select TraceID=@TraceID
goto finish

error: 
select ErrorCode=@rc

finish: 
go

If I try to run this script, it will fail. The scripting process doesn’t exactly mirror the GUI configuration of my trace. So before I get into how to run this script off hours let me review the different pieces of this script in a little more detail. If you look at this trace definition script in detail, you will notice that there are three different stored procedures that are executed: sp_trace_create, sp_trace_setevent, and sp_trace_setstatus.

The “sp_trace_create” SP is used to identify the trace definition to SQL Server. When this script was created, it didn’t set all the parameters that I specified on the GUI above, like the output file name, and roller options. In addition, the stop time wasn’t in the middle of the night which isn’t what I want. Therefore, to get this script to mirror my trace specification I will need to change the “sp_trace_create” call to look like this:

set @DateTime = '2007-10-18 02:00:00.000' -- set an appropriate stop time
set @maxfilesize = 5
exec @rc = sp_trace_create @TraceID output, 2, N'C:\temp\AW_problem', @maxfilesize, @Datetime

Here I have modified the original script code by:

  • Identify the time in which Profiler will stop its trace by modifying the @DateTime variable value to 2 AM in the morning.
  • Set the TRACE_FILE_ROLLOVER option to 2, which means when my profiler trace reaches the max file size of 5 MB, Profiler will close the existing file and create a new one.
  • Specified an output file of “C:\temp\AW_problem”

Just a note here about the trace output file, when you specify a trace output file, and that file already exists the “sp_trace_create” execution will fail. You need to specify a file that doesn’t exist. Since I ran the GUI to create my Profiler trace script, the above file already exists. So I will need to delete this file prior to running my script. Profiler appends a “.trc” extension to the output file specified on the “sp_trace_create” call. This is why I left off the “.trc” extension when I specified the output file name.

The “sp_trace_setevent” SP calls in the above script are used to identify the events and columns I want to trace. In my case, I want to trace 4 different events and a number of columns for each. You should not have to modify this section of code in a generated Profiler script, unless you want to include or exclude events and columns after the script is generated.

The “sp_trace_setstatus” SP is used to change the status of a trace. There are 3 different statuses that can be set using this SP. You can “start” a trace that is not running, you can “stop” a running trace, or you can “close and delete” a trace that is not running. The script that is generated from the Profiler GUI will automatically start the trace. Depending on how you are going to launch this script, you may or may not need to change this option. For my demo, I will not need to change the parameters for this SP.

Running a Profiler Trace off Hours

Now that I have my Profiler trace script, I need to set up a process that will allow my script to start collecting data at a particular time in the middle of the night. So for this example let’s say I want to have my script run at 1 AM tomorrow morning and I want it to run for one hour. To do this I would create a SQL Server Agent job to start at 1 AM, which runs the above script. I just need to remember to set the filename and stop time (@DateTime) appropriately in the script within the job step. In my case, I set the stop time to be 2 AM in the morning.

Once I have set up my script setup, I place it in a SQL Server Agent Job, and then schedule the job to run at 1 AM in the morning. This allows me to go home knowing that SQL Server Agent will do my Profiler monitoring automatically off hours while I sleep.

Viewing the Saved Trace Data

Anytime after my SQL Agent job runs and the trace stops I can view the Profiler trace information that was collected. To view the trace, I start Profiler by clicking on the “File” option from the menu, then moving the mouse over the “Open” item, and finally selecting the “File Trace” from the drop down menu. When I do this, a file open dialog is displayed allowing me to browse to the location where my SQL Server Agent created my off hours trace file that I identified in my Profiler script.

Conclusion

If you have performance problems off hours, do you really want to come in to diagnosis what is happening on your SQL Server machine? Generating a Profile script and running it off hours allows you to capture what is happening inside of SQL Server without actively monitoring SQL Server from your desktop. Don’t lose sleep next time you want to monitor something off hours, instead script out a Profiler trace, and launch the trace using a SQL Agent job.

» See All Articles by Columnist Gregory A. Larsen



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