ocp1z0-047: Basic concepts: Synonyms, dynamic performance view, data dictionary view

Answer a is right, come to your official explanation:

User_synonyms

User_synonyms describes theprivate synonyms (synonyms owned by the "Current user"). Its columns () are thesame as those in all_synonyms.

The test is as follows: Create two synonyms: one is public, the other is private, and then the query

Gyj@ocm> createsynonym emp1 for hr.employees;

Synonym created.

gyj@ocm> createpublic synonym emp2 for hr.employees;

Synonym created.

gyj@ocm> Select *from user_synonyms;

Synonym_name Table_owner table_name Db_link

------------------------------------------------------------ --------------------------------------------------- -----------------------------------------------------------------------------------------------------------

EMP1 HR EMPLOYEES

Answer b is wrong, the test is as follows:

Gyj@ocm> Conn System/oracle

Connected.

System@ocm> select * from tab$;

SELECT * FROM tab$

*

ERROR at line 1:

Ora-00942:table or view does not exist

In addition to the SYS user can access the base table, other users cannot ...

The answer c is also wrong, except SYS can access all users of the database, the other cannot ...

From official documents:

About Dynamic Performance views

Oracle contains a setof underlying views this are maintained by the database server and accessibleto the database administ Rator user SYS. These views are are calleddynamicperformance views because they are continuously updated while a database isopen and. nd their contents relate primarily to performance.

Although these viewsappear to is regular database tables, they are not. These views provide data oninternal disk structures and memory structures. You can select from Theseviews, but can never update or alter them.

v$ views

The actual dynamic performance views are identified bythe prefix. Public synonyms for the views have theprefixv$. Database administrators and other users should access only thev$objects, not thev_$ objects.

The answer d is also wrong, from the official explanation:

User_objects describes all OBJECTS owned by the current user. Its columns are the Sameas those in "all_objects".

Answer e is right, from an official explanation:

The data dictionary tables are not directly accessible, butyou can access information the them in through the data dictionary views. To list Thedata dictionary views available to you, query the viewdictionary.

Many data dictionary tables have three correspondingviews:

· An all_view displays "all" the information accessible to the "current user", includinginformation from the current user ' s Sche Ma as as as information from objectsin other schemas, if the current user has access to those objects by way ofgrants of privileges or roles.

· A Dba_view displays all relevant information in the entire database. Dba_ views are intended only for administrators. They can be accessed to byusers with theselect any TABLE privilege. This privilege was assigned to THEDBA in the system is initially installed.

· A User_view Displays all the information from the schema of the "current USER." Nospecial privileges are required to query.

The columns of Theall_,dba_, anduser_ views corresponding to a single data dictionary table are usually. Therefore, these views are are described in ' full ' once in Thischapter, at their A-occurrence, and alphabetically L Isted without fulldescriptions at their and other occurrences.

Answer: AE

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