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.
IO_COMPLETION Wait Stats: Spills, Sorts and File Growth
IO_COMPLETION wait stats measure queries waiting on disk work that isn’t a normal data page read, such as sorts and hashes that spill to tempdb. On Night 10 at the Clipboard Diner, a sheet cake for twelve turns out to be for sixty. Learn why spills happen, how to find them, and what SQL Server 2022 changed for log file growth.
PAGEIOLATCH Wait Stats: Waiting for Data From Disk
PAGEIOLATCH wait stats measure queries waiting while data pages are read from disk into memory. On Night 9 at the Clipboard Diner, the prep counter is too small for the menu and the cooks keep sending for things from the basement. Learn the two causes, how to read file latency per file, and the fixes in order.
SOS_SCHEDULER_YIELD Wait Stats: Reading CPU Pressure
SOS_SCHEDULER_YIELD wait stats count the moments a query gives up the CPU after its 4 ms turn and waits to get it back. On Night 8 at the Clipboard Diner, every cook steps on and off the burners all night. Learn when this wait is harmless, when it means CPU pressure, and how to find the queries that burn the most CPU.
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.