[Oracle] About Lock and Latch

[Oracle] Let's Talk About Lock and Latch. First, let's talk about what they have in common: they are essentially an exclusive Lock on resources, all caused by concurrency (if the database has only one session, ). Next, let's talk about their differences: first, they have different purposes. enqueue (Lock, Oracle official documentation uses these two terms in a mix, and a lot of enqueue can be seen while waiting for the event, actually, it is lock) to solve the data contention at the business layer, while latch is to solve the contention for memory resources. Second, they run in different ways. enqueue uses the queuing method, first come first served, while latch's competition is almost unordered. In a random way, first come first served, not necessarily first served, instead of being snatched, in addition, it is also a time slice round training method that won't be occupied all the time. It is not finished yet, and the time slice is one to one. Third, the session length is different. enqueue may hold the session for a long time based on the business situation, while latch is usually very short. Fourth, the cause is different. Too many enqueue is usually a problem of business design, while too many latch are, it is generally a problem at the database level (for example, no Bound variables, tables, or index hot blocks are used ).