Examine the following command: CREATE TABLE (prod_id number(4), Prod_name varchar2 (20), Category_id number(30), Quantity_on_hand number (3) INVISIBLE); Which three statements are true about using an invisible column in the PRODUCTS table?（）

A

The %ROWTYPE attribute declarations in PL/SQL to access a row will not display the invisible column in the output.

B

The DESCRIBE commands in SQL *Plus will not display the invisible column in the output.

C

Referential integrity constraint cannot be set on the invisible column.

D

The invisible column cannot be made visible and can only be marked as unused.

E

A primary key constraint can be added on the invisible column.

进程监视进程（PMON）的作用是什么？

Which CLI command is used to set a Privileged Exec password of my password?（）

A、 A

B、 B

C、 C

D、 D

有以下程序#include #include void fun(int*p1,int*p2,int*s){　s=(int*)malloc(sizeof(int));　*s=*p1+*p2;}main(){　int a[2]={1,2}, b[2]={10,20},*s=a;　fun(a,b,s);　printf("%d",*s);}程序运行后的输出结果是（　　）。

A、1

B、10

C、11

D、2

无线网络规划的目标是实现GSM网络在下列那些方面的良好平衡。（）

A、覆盖

B、容量

C、质量

D、成本

You performed an incremental level 0 backup of a database: RMAN > BACKUP INCREMENTAL LEVEL 0 DATABASE; To enable block change tracking after the incremental level 0 backup, you issued this command: SQL > ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE ‘ /mydir/rman_change_track.f’; To perform an incremental level 1 cumulative backup, you issued this command: RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE; Which three statements are true?（）

Backup change tracking will sometimes reduce I/O performed during cumulative incremental backups.

The change tracking file must always be backed up when you perform a full database backup.

Block change tracking will always reduce I/O performed during cumulative incremental backups.

More than one database block may be read by an incremental backup for a change made to a single block.

The incremental level 1 backup that immediately follows the enabling of block change tracking will not read the change tracking file to discover changed blocks.