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.
Wait Stats Explained: SQL Server as an All-Night Diner
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.
When Auto Update Statistics Is Not Enough
Auto update statistics can miss important data patterns; inspect thresholds, ascending keys, sampling, and targeted update schedules.
LIKE Cardinality: String Statistics and Row Estimates
LIKE row estimates depend on the pattern, string statistics and compilation context. Compare estimated and actual matching rows in a controlled distribution, while keeping cardinality estimates separate from the chosen access path.
Setting MAXDOP and Cost Threshold Sensibly
MAXDOP and cost threshold work together to shape parallel plans; inspect current values, test a change, and watch real workload effects.
NO_PERFORMANCE_SPOOL: Compare the Work Before Keeping the Hint
NO_PERFORMANCE_SPOOL changes one query optimization decision. A guarded private fixture compares baseline work, the optional hint and a supporting inner index. The article explains how to preserve results and assess actual child work without promising a plan shape.
Wait Statistics: Read the Snapshot Before Naming the Bottleneck
Wait statistics provide a starting point for investigation. Separate cumulative completed waits, background activity, signal time and currently waiting requests before treating the largest total as the present bottleneck.