Locking and UNDO

Problem:  What if deadlock while executing UNDO
Cannot abort UNDO -- transaction already aborting
Good news:  Record locks held to end of transaction
Will still be held at time of abort
Bad news:  Page-level locks (false sharing)
UNDO transactions marked as ``Golden''
Only one ``golden'' transaction executes at a time
Always abort the non-golden xaction after deadlock
More bad news:  What about during restart
No locking during restart
All transactions recovered sequentially