Wait statistics

Wait statistics show where SQL Server spends its time when it isn't computing. They are the fastest way to narrow down a bottleneck: instead of guessing, you see directly whether a system is waiting on CPU, I/O, locks or the network.

Live delta vs. cumulative

SQL Server accumulates waits since the last restart, which blurs the current picture. The Performance → Waits page therefore offers a live delta mode: it takes two snapshots with a short wait in between and shows only the difference – i.e. what is happening right now.

Filtering out idle waits

Many wait types are harmless (background tasks waiting for work). These idle waits are hidden by default so they don't drown out the real bottlenecks. You can also maintain your own suppress list (stored in the browser).

Categories

Wait types are grouped into categories (e.g. locks, I/O, CPU, network) to make patterns easier to spot. A high share in one category is the starting point for root-cause analysis – not the diagnosis itself.

Tip: wait stats tell you what is being waited on, not why. Combine them with Active Queries, Blocking and Query Analysis to get from symptom to cause.