Regarding redo/undo files.

Hi,
I went thru the site
http://www.postgresql.org/docs/7.4/static/wal-benefits-later.html
Undo operation is not implemented. and information of
the status regarding the transaction is stored in the
permanent file pg_clog. But I have not been able to
see the format of the file, as this file is in binary
format. Same for the redo file.
Could you please send me the format of the redo and
pg_clog file. Also, give me some idea as to what do we
need to change to implement undo-file. 
Thanks
Mamta 

________________________________________________________________________
Yahoo! India Matrimony: Find your life partner online
Go to: http://yahoo.shaadi.com/india-matrimony