log manager in ORACLE?

Hi,
I am using Oracle 8i EE.
I took a quick view of oracle books. I haven't found a direct answer for my questions.
I just want to know how log manager works in Oracle?

For example, when I issue one update sql request,

1. Oracle read the datablock from datafiles on disk into buffer. Before update data block, oracle first write the before and after image to log buffer?
2. When and what information will be written to Rollback Segments?
3. When the transaction end or the log buffer pool full, log buffer pool flush to redo log files?
4. The rollback segments will only keep before and after image for open transactions. Is that correct? The redo log files will store the before and after image of unactive transactions. Is that correct?

Thanks for any help?
Y Received on Mon Feb 11 2002 - 20:44:41 CST