Ankit Aggarwal

 Profile Answers by Ankit Aggarwal 

• May 7th, 2011

 

locks protect data during transactions, another process, latching, controls access to physical pages.

Latches are very lightweight, short-term synchronization objects protecting actions that do not need to be locked for the life of a transaction.

Nishanth

• Mar 14th, 2016

 

The difference between the two is that Locks are queueing mechanisms while Latches are not.
If two processes are spinning and waiting on a latch (access to a shared memory resource) and the resource protected by the latch becomes free (is released/unpinned by the holder), then whichever of the two waiters "wakes up" first from its spin gets the Latch. This is serialisation in the sense of "only one person at a time".
In an Lock -- eg shared locks on a table -- the access is granted on "first come first served". This is serialisation in the sense "access is via a Queue". That is why we can build a "lock tree" but not a "latch tree".

Sri

• Aug 16th, 2017

 

Locks are to maintain read consistency and will be applied on tables and the same kind on instance memory structures is called latch.