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.
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.
Live Wait Stats: What Is Waiting Right Now
Live wait stats show what every request in SQL Server is waiting on at this moment, and who is in its way. On Night 4 at the Clipboard Diner, the Saturday rush stalls behind a party in booth 7 that isn’t waiting for anything. Then three queries find the waiting tasks, the head blocker and one session’s own waits.
sys.dm_os_wait_stats: Reading the Wait Stats List
sys.dm_os_wait_stats is the running list of every wait SQL Server has recorded since its last restart. On Night 3 at the Clipboard Diner, Casey reads the clipboard at 2 AM and crosses out the sleepers. Then one query filters out the harmless waits and shows the share, the average and the signal part of every wait that matters.
Signal Wait Stats: CPU Waits vs Resource Waits
Signal wait stats show how long a SQL Server query sat ready to run, waiting in line for a CPU. On Night 2 at the Clipboard Diner, the potatoes arrive on time and the Garden Hash waits anyway. Then two queries split your server’s waits into the CPU part and the resource part.