Thanks for the research and posting the answer. Regarding the second point, Steve Adams said the same in his 16 March 2000 Q&A:
http://www.ixora.com.au/q+a/undo.htm
"Multiple transactions can share an undo block, but only in series, not concurrently."
Yong Huang 发表于 2015-9-14 23:27
Thanks for the research and posting the answer. Regarding the second point, Steve Adams said the sam ...
Thanks!
I thought *newing* is the only way that Oracle uses undo blocks forgetting that Oracle can also pick free undo blocks from free pool if there're any in it~~