Startup Options - view

[nkumarin001]

Hi,
Please any one answer this question.

1) Why we cant access or describe views related to USER,ALL,DBA when instance is started using STARTUP NOMOUNT,MOUNT?
For example views like user_objects,user_tables,all_sequences,dba_objects etc?

2) Why we can only access or describe Dictionary views when INSTANCE is started using STARTUP NOMOUNT,MOUNT?
For example Dictionary views like v$datafile,v$controlfile etc?

Regards,
Naveen

[nkumarin001]

Hi,
I tried a lot for this question, but i dint got the answer. Please any one answer this question.

1) Why we cant access or describe views related to USER,ALL,DBA when instance is started using STARTUP NOMOUNT,MOUNT?
For example views like user_objects,user_tables,all_sequences,dba_objects etc?

2) Why we can only access or describe Dictionary views when INSTANCE is started using STARTUP NOMOUNT,MOUNT?
For example Dictionary views like v$datafile,v$controlfile etc?

Regards,
Naveen

[debasisdas]

All the data dictionary views are available only after database is open as oracle checks the consistency of all objects (tables, indexes etc) only when the database is in the OPEN mode and not in NOMOUNT and MOUNT stages. In the NOMOUNT stage only the instance is started and in the MOUNT stage it checks and validates the controlfile, hence the answer to your second question as why v$datafile and v$controlfile are available on the MOUNT stage. Also these views are useful for DBA to perform any recovery if required.