Why should you care?

“It is slow” becomes “buffer pool miss” or “page latch” when you know the moving parts.

See it live — copy this example

Run in SQL Server Management Studio (SSMS) or Azure Data Studio.

SELECT
    (physical_memory_kb / 1024) AS MemoryMB,
    committed_kb / 1024 AS CommittedMB
FROM sys.dm_os_sys_info;
SELECT TOP (10) wait_type, wait_time_ms
FROM sys.dm_os_wait_stats
WHERE wait_type NOT LIKE '%SLEEP%'
ORDER BY wait_time_ms DESC;

What happened?

• Memory figures show the OS view SQL Server sees.
• Top waits hint whether IO, CPU, or locking dominates — your internals compass.

Practice next

1. Run memory and wait queries.
2. Relate PAGEIOLATCH waits to disk speed.
3. Open a plan and connect operators to pages/rows conceptually.
4. Check sys.dm_os_buffer_descriptors counts per database.
5. Note checkpoint and lazywriter at a high level.

Remember

Pages live in the buffer pool when hot. Waits diagnose subsystems. Internals support evidence-based tuning.

Latch waits on tempdb

DataVerse heavy sorts flooded tempdb; waits pointed there.

Outcome: Team added tempdb files and reduced spills.