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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.

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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.

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