多项选择题
A.The backup performed on Sundays contains all the blocks that have ever been used in the database.
B.The backup performed on Sundays contains all the blocks that have changed since the last level 1 backup.
C.The backup performed on each working day contains all the blocks that have changed since the last level 0 backup.
D.The backup performed on Monday contains all the blocks that have changed since the level 0 backup， and every other working day contains all the blocks that have changed since the level 1 backup
多项选择题 You receive complaints from users regarding the high waiting time for their transactions. Oninvestigation， you find that some users are not committing their transactions though they are notperforming any activity for a long time. As a result， SQL statements need to wait for row-level locks. Which two actions could you take to prevent this locking problem in the future（）
多项选择题 WhichtwostatementsdescribegoodpracticesforanapplicationdevelopertoreducelockingconflictsinOracledatabase（）
单项选择题 User A executes the following command to drop a large table in your database： SQL> DROP TABLE trans； While the drop table operation is in progress， user B executes the following command on the same table： SQL> DELETE FROM trans WHERE tr_type=’SL’； Which statement is true regarding the DELETE command（）