Troubleshooting SQL Server Slowness

The first step in diagnosing SQL Server performance is to determine the physical bottleneck with the most contention. Contention in one of the following areas does not always mean that subsystem is performing poorly. It could just as well be improper utilization due to poor tuning. Nevertheless, identifying the bottleneck is always the first place to start. Luckily, Microsoft does provide some unsupported but very useful tools to help us find this. For these, see the video Using SQLDiag and SQL Nexus. I still recommend reading the article below, as it will help understand the interrelation between subsystems. There are ten main bottlenecks that can cause SQL Server to slow down. They are all interrelated and often fixing one causes another bottleneck to be revealed. CPU Memory Disk Paging Blocking Network IO Process Trimming Old Statistics Fragmentation Recompilation Blocking Blocking is caused by contention of resources. To understand blocking you need to understand locking. Locking occurs in order to ensure users see up-to-date accurate information. If records being updated are also being shown to a user before the update finishes, then inaccurate information is being displayed. The most common reason for blocking is the lack of indexing or queries not written to utilize existing indexes. They mostly occur when update or delete statements are performing a table scan, while an incompatible lock like a select statement tries to read the same records. This script will Show the blocking process This script will show the table involved in the blocking And […]