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During the Saturday rush Casey asks each ticket what it waits for, finds three orders stuck behind a finished party in the corner booth, and clears the booth so Ace can fire all three plates. Casey says, "The quiet booth was the head blocker."

Live Wait Stats: What Is Waiting Right Now

February 4, 2011
Pinal Dave
SQL Performance
SQL DMV, SQL Lock, SQL Scripts, SQL Wait Stats

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.

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Late at night Casey reads the whole clipboard, finds the biggest line belongs to the sleeping night baker, and slashes it out with a giant red pen while Ace and Quinn duck. Casey says, "Cross out the sleepers first. Then read."

sys.dm_os_wait_stats: Reading the Wait Stats List

February 3, 2011
Pinal Dave
SQL Performance
SQL DMV, SQL Performance, SQL Scripts, SQL Wait Stats

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.

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Kit gets the potatoes fast, but every burner is busy, so the order waits on the rail while the potatoes grow bored little faces and Casey hangs a second stopwatch. Quinn sums it up: "Ready to cook, stuck in line. That's a signal wait!"

Signal Wait Stats: CPU Waits vs Resource Waits

February 2, 2011
Pinal Dave
SQL Performance
SQL CPU, SQL DMV, SQL Scripts, SQL Wait Stats

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.

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A postcard says the food critic is coming, the busy kitchen can't explain its late plates, and Casey hangs up a new clipboard while Ace, Quinn and even the jukebox lean in. Casey asks, "New question. What are we waiting for?"

Wait Stats Explained: SQL Server as an All-Night Diner

February 1, 2011
Pinal Dave
SQL Performance
SQL DMV, SQL Performance, SQL Wait Stats

Wait stats explained with one picture: SQL Server is an all-night diner, and every query is an order ticket that waits for something. Meet the Clipboard Diner, its owner Casey, the cooks and booth 7. Then count the burners and cooks on your own server with one query.

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Casey times one Garden Hash: Ace stalls at an empty potato bin, and by the time Quinn serves the plate, a cobweb has grown on the trucker's coffee cup. Casey reads the stopwatch: "Cooking: four minutes. Waiting: nine."

Wait Stats Basics: How Waits Work in SQL Server

February 1, 2011
Pinal Dave
SQL Performance
SQL DMV, SQL Scripts, SQL Wait Stats

Wait stats basics start with one idea: a query in SQL Server is always either working or waiting. On Night 1 at the Clipboard Diner, one plate of Garden Hash shows the three states every query moves through. Then two queries show the same thing on your own server.

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Bees crowding one narrow entrance of a wooden beehive while a second opening on the side stays almost empty.

High-Frequency Inserts Without Blocking

September 16, 2009
Pinal Dave
SQL Performance
SQL Index, SQL Lock, SQL Server, SQL Wait Stats, Transaction Log

High-frequency inserts can stall on the log, indexes, or last-page contention; learn to diagnose the wait and choose targeted SQL Server fixes.

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Gouache painting of a single small red crane on a quay with a long line of crates waiting to be moved

Measure CPU Pressure in SQL Server with Waits and Schedulers

August 17, 2009
Pinal Dave
SQL Performance
SQL CPU, SQL DMV, SQL Wait Stats

CPU Pressure means tasks are ready to run but every scheduler is busy, so they wait in a queue. This post reads that queue from the schedulers, compares signal waits with resource waits, checks recent CPU history and finds the queries that use the most CPU. It ends with a plain way to decide between a faster CPU, more cores and better queries.

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