今天在做测试的时候想查询数据文件对应的表空间信息，desc dba_Data_files视图时发现报不存在这个对象。当时以为自己的DB在mount下没法查询是正常的，后来在DB OPEN下查询 dba_data_files还是报不存在这个对象。顿时感觉疑惑了，其他对象都查询正常，唯独DBA_*的视图都不能正常查询使用。查询MOS(文档 ID 296235.1) 发现如下描述：

cuug本周五晚免费Oracle网络公开课《人生最痛苦的事：人还在钱没了――守护数据库的备份信息》

APPLIES TO:

Oracle Database - Enterprise Edition - Version 8.1.7.4 to 11.2.0.1 [Release 8.1.7 to 11.2]

Information in this document applies to any platform.

SYMPTOMS

If you describe any DBA_* Views (Data dictionary views) in a mount stage, than you will not be able to

describe those views even after opening the database.

You can test as follows:

+ Shutdown the database.

SQL> Shutdown immediate

+ Mount the database.

SQL> Startup Mount

+ Describe any Data Dictionary view.

SQL> DESC DBA_DATA_FILES

ERROR:

ORA-04043: object DBA_DATA_FILES does not exist.

+ Open the Database.

SQL> ALTER DATABASE OPEN;

Database altered

+ Describe the same Data Dictionary view.

SQL> DESC DBA_DATA_FILES

ERROR:

ORA-04043: object DBA_DATA_FILES does not exist

*** Error will appear till we bounce the Database / flush the shared pool.

CAUSE

This is related to Bug 2365821

Abstract: ORA-4043 ON DBA_* TABLES IF THEY ARE DESCRIBED IN A MOUNT STAGE.

SOLUTION

Available workarounds are:

1) Don't describe the dba_* views at mount stage.

OR

2) If you issue DESC of any DBA_*views at mount stage, then shutdown and restart the DB instance.

OR

3) Flush the shared pool.

SQL> Alter system flush shared_pool;

and then reissue the failing command.

正是由于我在数据库mount状态下查询dba_data_files视图，导致遭遇oracle 数据库产品的Bug 2365821，数据库即使OPEN下也不能正常使用dba_*视图。