What are the SQL Server Counters for monitoring SQL Server Performance?
Top 10 SQL Server Counters for Monitoring SQL Server Performance
Do you have a list of SQL Server Counters you review when monitoring
your SQL Server environment? Counters allow you a method to measure
current performance, as well as performance over time. Identifying the
metrics you like to use to measure SQL Server performance and collecting
them over time gives you a quick and easy way to identify SQL Server
problems, as well as graph your performance trend over time.
Below is my top 10 list of SQL Server counters in no particular order.
For each counter I have described what it is, and in some cases I have
described the ideal value of these counters. This list should give you a
starting point for developing the metrics you want to use to measure
database performance in your SQL Server environment.
1. SQLServer: Buffer Manager: Buffer cache hit ratio
The buffer cache hit ratio counter represents how often SQL Server is
able to find data pages in its buffer cache when a query needs a data
page. The higher this number the better, because it means SQL Server was
able to get data for queries out of memory instead of reading from
disk. You want this number to be as close to 100 as possible. Having
this counter at 100 means that 100% of the time SQL Server has found the
needed data pages in memory. A low buffer cache hit ratio could
indicate a memory problem.
2. SQLServer: Buffer Manager: Page life expectancy
The page life expectancy counter measures how long pages stay in the
buffer cache in seconds. The longer a page stays in memory, the more
likely SQL Server will not need to read from disk to resolve a query.
You should watch this counter over time to determine a baseline for what
is normal in your database environment. Some say anything below 300 (or
5 minutes) means you might need additional memory.
3. SQLServer: SQL Statistics: Batch Requests/Sec
Batch Requests/Sec measures the number of batches SQL Server is
receiving per second. This counter is a good indicator of how much
activity is being processed by your SQL Server box. The higher the
number, the more queries are being executed on your box. Like many
counters, there is no single number that can be used universally to
indicate your machine is too busy. Today’s machines are getting more and
more powerful all the time and therefore can process more batch
requests per second. You should review this counter over time to
determine a baseline number for your environment.
4. SQLServer: SQL Statistics: SQL Compilations/Sec
The SQL Compilations/Sec measure the number of times SQL Server compiles
an execution plan per second. Compiling an execution plan is a
resource-intensive operation. Compilations/Sec should be compared with
the number of Batch Requests/Sec to get an indication of whether or not
complications might be hurting your performance. To do that, divide the
number of batch requests by the number of compiles per second to give
you a ratio of the number of batches executed per compile. Ideally you
want to have one compile per every 10 batch requests.
5. SQLServer: SQL Statistics: SQL Re-Compilations/Sec
When the execution plan is invalidated due to some significant event,
SQL Server will re-compile it. The Re-compilations/Sec counter measures
the number of time a re-compile event was triggered per second.
Re-compiles, like compiles, are expensive operations so you want to
minimize the number of re-compiles. Ideally you want to keep this
counter less than 10% of the number of Compilations/Sec.
6. SQLServer: General Statistics: User Connections
The user connections counter identifies the number of different users
that are connected to SQL Server at the time the sample was taken. You
need to watch this counter over time to understand your baseline user
connection numbers. Once you have some idea of your high and low water
marks during normal usage of your system, you can then look for times
when this counter exceeds the high and low marks. If the value of this
counter goes down and the load on the system is the same, then you might
have a bottleneck that is not allowing your server to handle the normal
load. Keep in mind though that this counter value might go down just
because less people are using your SQL Server instance.
7. SQLServer: Locks: Lock Waits / Sec: _Total
In order for SQL Server to manage concurrent users on the system, SQL
Server needs to lock resources from time to time. The lock waits per
second counter tracks the number of times per second that SQL Server is
not able to retain a lock right away for a resource. Ideally you don't
want any request to wait for a lock. Therefore you want to keep this
counter at zero, or close to zero at all times.
8. SQLServer: Access Methods: Page Splits / Sec
This counter measures the number of times SQL Server had to split a page
when updating or inserting data per second. Page splits are expensive,
and cause your table to perform more poorly due to fragmentation.
Therefore, the fewer page splits you have the better your system will
perform. Ideally this counter should be less than 20% of the batch
requests per second.
9. SQLServer: General Statistic: Processes Block
The processes blocked counter identifies the number of blocked
processes. When one process is blocking another process, the blocked
process cannot move forward with its execution plan until the resource
that is causing it to wait is freed up. Ideally you don't want to see
any blocked processes. When processes are being blocked you should
investigate.
10. SQLServer: Buffer Manager: Checkpoint Pages / Sec
The checkpoint pages per second counter measures the number of pages
written to disk by a checkpoint operation. You should watch this
counter over time to establish a baseline for your systems. Once a
baseline value has been established you can watch this value to see if
it is climbing. If this counter is climbing, it might mean you are
running into memory pressures that are causing dirty pages to be flushed
to disk more frequently than normal.
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