Why aeron`s logbuffers divide into three selections?
Each term can be in one of three logical states:
clean terms have yet to have data written to them, an active term is where data is being written to, and dirty terms hold data that is no longer active, but is temporarily available for retransmission.
why one selection is not work?
There are many reasons to why Aeron uses 3 buffers in rotation for a message stream. It is best to start with the talk referenced below and then look for other talks I have publicly given. The main points are that it enables an algorithm which is wait-free for concurrent publication and supports retransmits on the network in the event of loss.
https://www.youtube.com/watch?v=tM4YskS94b0