What is Latch in SQL Server?

Question

What is Latch? Why we use latch? Why we need latch? Please give me more examples.

Answer 1

Hi @Rabia Kurnaz ,

A latch is a lightweight synchronization object used by the Storage Engine of SQL Server to protect internal memory structures that can’t be accessed in a true multi-threaded fashion. In the first part of the blog posting I will talk about why there is a need for latches in SQL Server, and in the second part I will introduce various latch types to you, and how you can troubleshoot them.
For more details, please see:
https://www.watelectronics.com/what-is-a-latch-different-types-and-their-applications/
https://www.sqlpassion.at/archive/2014/06/23/introduction-to-latches-in-sql-server/#:~:text=A%20latch%20is%20a%20lightweight%20synchronization%20object%20used,can%E2%80%99t%20be%20accessed%20in%20a%20true%20multi-threaded%20fashion.

Best regards
Niko

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Answer 2

I suggest you read this:

https://www.sqlshack.com/all-about-latches-in-sql-server/

Answer 3

You don't "use latches", that are performance counters for waits, see
https://learn.microsoft.com/en-us/sql/relational-databases/performance-monitor/sql-server-latches-object?view=sql-server-ver16