RESOURCE_SEMAPHORE wait stats mean a query is waiting for memory before it can even start. On Night 25 at the Clipboard Diner, a wedding party reserves the whole counter and two birthday parties wait. Then I show how to find waiting grants, why grants grow too big, and the fixes I try first.
ASYNC_NETWORK_IO Wait Stats: When the Application Is Slow
ASYNC_NETWORK_IO wait stats mean SQL Server has results ready and is waiting for the application to read them. On Night 21 at the Clipboard Diner, hot plates pile up at the pass while Quinn tells a long story at table 4. Learn the causes in the order I find them, two queries that name the slow program, and why the fixes live in the application.
Harmless Wait Stats: Waits You Can Safely Ignore
Harmless wait stats come from background tasks that sleep on purpose, such as the lazy writer, the deadlock monitor and the full-text scheduler. On Night 13 at the Clipboard Diner, the biggest numbers on Casey’s clipboard belong to a sleeping baker and an idle dishwasher. Two queries show how much of your wait list they take up and how to judge an unknown wait yourself.
ASYNC_IO_COMPLETION Wait Stats: Large File Operations
ASYNC_IO_COMPLETION wait stats measure the time SQL Server waits for big file jobs: backups, restores and new data file space. On Night 11 at the Clipboard Diner, the night truck and a freshly painted shelf show which part is normal and which part you can remove. One setting, instant file initialization, removes most of the avoidable waiting.
Parallelism Wait Stats: Tuning MAXDOP and Cost Threshold
Parallelism wait stats drop when two settings fit your server: cost threshold for parallelism decides which queries go parallel, and MAXDOP decides how many threads they get. On Night 7 at the Clipboard Diner, Casey writes two house rules for big parties. Then the kitchen starts learning on its own, the way DOP feedback does in SQL Server 2025 Enterprise.
CXPACKET Wait Stats: What Parallel Waits Mean
CXPACKET wait stats measure the threads of a parallel query waiting on each other. On Night 6 at the Clipboard Diner, a tour bus of forty shows why splitting work helps, and how one overloaded cook holds everyone up. Learn CXPACKET, CXCONSUMER and the two CXSYNC waits, and how to spot skew.
Wait Stats Over Time: Measuring One Time Window
Wait stats over time means measuring the waits of one window, such as your busy hour, instead of reading totals since the last restart. On Night 5 at the Clipboard Diner, Casey photographs the clipboard at 6:00 and at 7:00 and subtracts. Then one script does the same thing with two snapshots of sys.dm_os_wait_stats.