If your making money taking care of someones DB than you should either invest 100 $ on a few books or get used to searching google for the manuals and guides which are replicated all over the net.

Here is a link that I got by searching for " redo logs oracle" at [url]http://www.google.com:[/url]

[url]http://docs.rinet.ru:8083/O8/ch06/ch06.htm[/url]

It has more than you ever want to know about redo logs.

-Roger