Latches what are they...

Hi
what are the latches. I have read the documents and oracle documents describe that oracle latch are light weight locks. but when i investigate i found out the latches have latch addr and chain# what are they.
thanks
Nick

so latches are associated with processes. Am i
right?
for example if one process want to share the data of
another process he will put a lock on the share data
area and no other process can access itNot the way I like to think about it.
For me, Latches are associated with memory data structures. A process may acquire a latch for a short period of time.
Analogy: wedding ... guest book ... 'wedding' pen linked to book by a chain.
Data store = guest book
Latch = pen
Guest 1 comes by ... pen is free, guest 'acquires' pen and signs book
Guest 2 comes by ... pen is in use, guest goes away to come back a bit later
Guest 3 comes by ... pen is now free, guest acquires pen (note guest 2 was off doing something else)
Guest 4 comes by ... pen is busy
Guest 2 comes by .... pen is free, guest acquires pen. ...
Is the pen associated with the guest, or with the book?

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