Performance monitoring overview

How can we define performance? We could say that it is the response time of a request. This means that we recognize which query, database, or whole instance of SQL Server is performing poorly while the response time (from the moment the request was sent by the session until the response information was received by the session) becomes unacceptable by the client. It can be caused by many factors, such as poor query syntax, missing indexes, or even network misconfiguration.

While monitoring and tuning the performance, we must not just measure the response times but also many factors affecting the performance. What's more, we need to find out the root cause for why the system slows down. Based on previous experience, it is good to consider the following points:

• Number of requests: Just a benchmark value that affects the level of concurrency on data and CPUs used by requests.
• Space affected by the request: How much data is moved between...