SQL> desc dba_objects;
ERROR:
ORA-04043: object dba_objects does not exist

SQL> select status from v$instance;

STATUS
------------------------
STARTED

SQL> alter database mount;

Database altered.

SQL> alter database open;

Database altered.

SQL> desc dba_objects;
ERROR:
ORA-04043: object dba_objects does not exist

SQL> desc dba_data_files;
ERROR:
ORA-04043: object dba_data_files does not exist

SQL> shutdown immediate;
数据库已经关闭。
已经卸载数据库。
ORACLE 例程已经关闭。
SQL> startup
ORACLE 例程已经启动。

Total System Global Area 411041792 bytes
Fixed Size                  1249272 bytes
Variable Size             138412040 bytes
Database Buffers          264241152 bytes
Redo Buffers                7139328 bytes
数据库装载完毕。
数据库已经打开。
SQL> desc dba_objects;
名称                                      是否为空? 类型
----------------------------------------- -------- ------------------------

OWNER                                              VARCHAR2(30)
OBJECT_NAME                                        VARCHAR2(128)
SUBOBJECT_NAME                                     VARCHAR2(30)
OBJECT_ID                                          NUMBER
DATA_OBJECT_ID                                     NUMBER
OBJECT_TYPE                                        VARCHAR2(19)
CREATED                                            DATE
LAST_DDL_TIME                                      DATE
TIMESTAMP                                          VARCHAR2(19)
STATUS                                             VARCHAR2(7)
TEMPORARY                                          VARCHAR2(1)
GENERATED                                          VARCHAR2(1)
SECONDARY                                          VARCHAR2(1)

SQL>