Oracle ARIES implementation

I have a question about Oracle internal processing of commit.

Here is excerpt from Oracle wits evenst description:

log file sync

When a user session commits, the session's redo information needs to be flushed to the redo logfile. The user session will post the LGWR to write the log buffer to the redo log file. When the LGWR has finished writing, it will post the user session.

I find it difficult to believe Oracle maintains redo sub-buffers for every session, does it?
As far as I understand, LGWR will write the whole redo buffer up to the commit SCN but not "the session's redo information" as the description states.  

Fyrirvari/Disclaimer
http://www.landsbanki.is/disclaimer

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