High-performing, high-availability databases are every SQL Server DBA’s goal, but the reality is that database performance isn’t always optimal. Slow response times, timeouts, and bogged-down CPUs happen to the best of us, which makes strategically configuring SQL Server diagnostics a crucial step in maintaining an efficient, well-functioning system.
SQL Server diagnostics will uncover performance issues related to memory usage, query speed and efficiency, and CPU usage, which will help you identify and remediate problems quickly with minimal effect on performance. To further minimize performance impacts, you can create a performance monitoring strategy that includes tracking diagnostic data over time to uncover hard-to-locate issues and predict future performance problems before they occur.
To get the most valuable information from your SQL Server diagnostics, it’s important to first identify what you hope to learn from the data so you monitor the most relevant performance metrics. Here are four tips to help you get started.
Diagnostic Goal: Monitor Database Performance for On-Premises, Virtual, and Cloud Environments
Whether your databases are housed on-premises, in the cloud, or in a hybrid environment, monitoring database performance in these five areas will alert you to some of the most common performance issues:
- Availability: Maintaining high availability is one of the DBA’s top priorities. Tracking failover cluster log data and current server status are key to detecting and correcting problems early.
- TempDB usage: Keep an eye on how much TempDB you use and how it’s being used. It’s also advisable to create a TempDB baseline and pull performance data before and after changes.
- I/O: SQL Server diagnostics will uncover stuck I/O operations that can cause blocking and other performance issues.
- CPU usage: High CPU usage can be caused by several things. Use SQL Server diagnostics to isolate the root cause. This checklist can point you in the right direction.
- Memory usage: If you aren’t optimizing memory usage, you will have performance issues at some point. Run diagnostics to determine which processes are using more than their share of memory and optimize or rewrite them as needed.
Diagnostic Goal: Find the Causes of Blocks and Deadlocks
Blocks and deadlocks are prime performance killers, so diagnosing what is causing blocks and resolving the problem quickly is essential to maintaining high performance. Several common sources of blocks and deadlocks can be eradicated via these three practices:
- Examine queries and query plans: Long queries and inefficient query plans contribute to blocks and deadlocks. Diagnostics can identify queries that can be broken down into multiple short transactions and which query plans aren’t optimized as a result of out-of-date statistics.
- Analyze workload: An increase in workload can cause blocks as more processes vie for the same resources. Diagnostics can pinpoint which user, database, host, or SQL Server statement is causing the block or deadlock so you can redistribute workload as needed.
- Check indexes: Good indexing can prevent blocks by removing the need for full table scans. By allowing SQL Server to seek rather than scan, indexing keeps non-locked resources accessible.
Diagnostic Goal: Address False Alerts
False alerts are more than just annoying; they contribute to undetected performance issues via alarm fatigue. Alarm fatigue occurs when frequent false alarms cause a DBA to ignore alerts, potentially missing a notification that a critical failure has occurred.
The best way to stop false alerts is diagnosing the sources of recurring false alerts and either removing non-critical alerts or setting thresholds that narrowly specify the conditions that trigger an alert.
Diagnostic Goal: Optimize SQL Queries
Running regular SQL Server diagnostics on queries will help reduce or eliminate a host of potential performance problems. Two ways you can improve queries based on SQL Server diagnostics are:
- Query tuning: If your SQL Server performance monitoring tool shows that a report is taking ages to generate, that there has been a huge spike in I/O wait recently, or that certain jobs are taking three times as long to run as they did a year ago, diagnostics may indicate query tuning is in order. Query tuning improves performance by analyzing queries and then rewriting them if necessary until they are running at their maximum level of efficiency.
- Updating statistics: As mentioned above, out-of-date statistics contribute to performance problems by triggering inefficient query plans. Schedule automated updates where possible. When automation isn’t possible, add manual updates to your regular maintenance checklist to ensure statistics stay current.
SQL Server diagnostics are an essential tool in the DBA’s toolbox. Understanding how diagnostics contribute to maintaining a reliable, high-availability SQL Server database environment will help you find and fix performance issues quickly with minimal effect on your users.