SQLDay2013_MaciejPilecki_Lock&Latches
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Locks are used to protect logical data integrity and are often held for the duration of a transaction. Latches synchronize access to internal server structures like buffer pages in cache and I/O operations. Spinlocks are lightweight locks that protect internal data structures and cause threads to "spin" rather than sleep during contention. All three concurrency structures are used for synchronization but differ in how they operate and the level and duration of the resources they protect.
SQLDay2013_MaciejPilecki_Lock&Latches
- 1. NASI SPONSORZY I PARTNERZY
- 2. SQL Server Concurrency Structures: Lock, Latches and Spinlocks Maciej Pilecki
- 3. Concurrency structures • Main concurrency structures in SQL Server: – Locks – Latches – Spinlocks • All are used to synchronize access to various structures but they differ in internals
- 4. Locks • • • • • • Used to protect LOGICAL integrity of data Often held for the duration of the transaction Lock granularity (ROW, PAGE, TABLE) Lock mode (S, U, X, IS, IX, Sch, etc.) Lock escalation Each lock type has corresponding wait type
- 5. Latches • Three main categories: – Buffer latches (latching pages in cache – PAGELATCH_*) – IO latches – used to synchronize I/O (PAGEIOLATCH_*) – Non-buffer latches (everything else – LATCH_*) • Each latch type has many corresponding wait types
- 6. Spinlocks • • • • • • Light-weight, short-lived synchronization primitives Used to protect internal server data structures sys.dm_os_spinlock_stats NO corresponding wait type! The thread DOES NOT sleep – it “spins” Hardest type of contention to troubleshoot
- 7. Concurrency structures • Main concurrency structures in SQL Server: – Locks – Latches – Spinlocks • All are used to synchronize access to various structures but they differ in internals
- 8. NASI SPONSORZY I PARTNERZY Organizacja: Polskie Stowarzyszenie Użytkowników SQL Server - PLSSUG Produkcja: DATA MASTER Maciej Pilecki