Buffer busy waits in Oracle

[satish]

Hi erman,

I have asked this question to few blogs but did nt get satisfied response.I hope,i will get it here and Here is my concern

When multiple sessions are requesting the blocks that reside in the disk, it takes too much time for a session to read it into the buffer cache. Other session(s) that need the same block will register ‘buffer busy wait’.

Is this true?If yes, I would like to understand why it takes too much time to read into the buffer cache?

Appreciate your efforts

[ErmanArslansOracleBlog]

*Read by other session/buffer busy - Waits related to contention on  hot blocks.
This wait happens when a session wants to access a database block in the buffer cache but it cannot as the buffer is "busy".
This wait event means either,
Another session is reading the block into the buffer. Starting with 10g this wait time is counted in read by other session wait.
or
Another session holds the buffer in an incompatible mode to our request.

&

It takes time, as we tell OS (drivers etc..) to retrive data.. So , there is code to be executed during the way. There is a significant latency when we try get a data residing in the disk.. It is  not like an inmemory operation.
Also, when we try to put a new buffer in the buffer cache, we have code to be executed, we need to check the right place to put it and so on..