多选题Which three operations require undo data（）Acommitting a transactionBflashing back a transactionCrecovering a failed transactionDrunning a read-consistent queryEchanging a tablespace status from READ ONLY to READ WRITE
题目
多选题
Which three operations require undo data（）
A
committing a transaction
B
flashing back a transaction
C
recovering a failed transaction
D
running a read-consistent query
E
changing a tablespace status from READ ONLY to READ WRITE