奇怪的v$database

xuhainanjing

HR@single_copy> SELECT OBJECT_NAME, OBJECT_TYPE from dba_objects where object_name='V$DATABASE';                 

OBJECT_NAME                              OBJECT_TYPE
---------------------------------------- -------------------
V$DATABASE                               SYNONYM                           


HR@single_copy> SELECT TABLE_OWNER,SYNONYM_NAME,TABLE_NAME FROM DBA_SYNONYMS WHERE SYNONYM_NAME='V$DATABASE';                           

TABLE_OWNER                    SYNONYM_NAME                   TABLE_NAME
------------------------------ ------------------------------ ------------------------------
SYS                            V$DATABASE                     V_$DATABASE


HR@single_copy> conn / as sysdba                                                     
Connected.
SYS@single_copy> select dbms_metadata.get_ddl('TABLE','V_$DATABASE') from dual;
ERROR:
ORA-31603: object "V_$DATABASE" of type TABLE not found in schema "SYS"
ORA-06512: at "SYS.DBMS_METADATA", line 1546
ORA-06512: at "SYS.DBMS_METADATA", line 1583
ORA-06512: at "SYS.DBMS_METADATA", line 1901
ORA-06512: at "SYS.DBMS_METADATA", line 2792
ORA-06512: at "SYS.DBMS_METADATA", line 4333
ORA-06512: at line 1

奇怪么？

xuhainanjing

SYS@single_copy> select view_name,text from dba_views where view_name='V_$DATABASE';

VIEW_NAME                      TEXT
------------------------------ --------------------------------------------------------------------------------
V_$DATABASE                    select "DBID","NAME","CREATED","RESETLOGS_CHANGE#","RESETLOGS_TIME","PRIOR_RESET
                               LOGS_CHANGE#","PRIOR_RESETLOGS_TIME","LOG_MODE","CHECKPOINT_CHANGE#","ARCHIVE_CH
                               ANGE#","CONTROLFILE_TYPE","CONTROLFILE_CREATED","CONTROLFILE_SEQUENCE#","CONTROL
                               FILE_CHANGE#","CONTROLFILE_TIME","OPEN_RESETLOGS","VERSION_TIME","OPEN_MODE","PR
                               OTECTION_MODE","PROTECTION_LEVEL","REMOTE_ARCHIVE","ACTIVATION#","SWITCHOVER#","
                               DATABASE_ROLE","ARCHIVELOG_CHANGE#","ARCHIVELOG_COMPRESSION","SWITCHOVER_STATUS"
                               ,"DATAGUARD_BROKER","GUARD_STATUS","SUPPLEMENTAL_LOG_DATA_MIN","SUPPLEMENTAL_LOG
                               _DATA_PK","SUPPLEMENTAL_LOG_DATA_UI","FORCE_LOGGING","PLATFORM_ID","PLATFORM_NAM
                               E","RECOVERY_TARGET_INCARNATION#","LAST_OPEN_INCARNATION#","CURRENT_SCN","FLASHB
                               ACK_ON","SUPPLEMENTAL_LOG_DATA_FK","SUPPLEMENTAL_LOG_DATA_ALL","DB_UNIQUE_NAME",
                               "STANDBY_BECAME_PRIMARY_SCN","FS_FAILOVER_STATUS","FS_FAILOVER_CURRENT_TARGET","
                               FS_FAILOVER_THRESHOLD","FS_FAILOVER_OBSERVER_PRESENT","FS_FAILOVER_OBSERVER_HOST
                               " from v$database

v_$database 到底是table,synonym, 还是view?