You started a long transaction. Before committing, you executed a query on one of the tables currently being modified. You received the following error:
ORA-01555: snapshot too old
How would you prevent such an error in the future? (Choose three.)
A. guarantee undo retention
B. add one more redo log group
C. size the redo log files appropriately
D. size the UNDO tablespace appropriately
E. size the SYSTEM tablespace appropriately
F. configure an appropriate undo retention interval
G. change automatic undo management to manual
Answer: ADF
ORA-01555: snapshot too old: rollback segment number string
ORA-01555: snapshot too old: rollback segment number string with name "string" too small
Cause: rollback records needed by a reader for consistent read are overwritten by other writers
Action: If in Automatic Undo Management mode, increase undo_retention setting. Otherwise, use larger rollback segments
A undo保留时间，D增加UNDO表空间大小，F是设置合理的保留周期。
其余选项都没有什么作用。
A undo保留时间，D增加UNDO表空间大小，F是设置合理的保留周期。
其余选项都没有什么作用。