Which statement is true about using the Export/Import method for migrating data when upgrading to Oracle
Database 12c?

The user SCOTT owns the CUST table that is placed in the SALES tablespace. The user SCOTT opens a
session and executes commands as follows:
SQL> INSERT INTO cust VALUES(101, 'JACK');
1 row created.
SQL> INSERT INTO cust VALUES(102, 'SMITH');
1 row created.
As a DBA, you execute the following command from another session:
ALTER TABLESPACE sales READ ONLY;
Which statement is true regarding the effect of this command on the transaction in Scott's session?

You configured the Fast Recovery Area (FRA) for your database. The database instance is in ARCHIVELOG mode. The default location for the archived redo log files is the FRA.
Which two files are removed automatically if space is required in the FRA as per the retention policy? (Choose two.)

Which two are prerequisites for performing a flashback transaction? (Choose two.)

The HR schema exists in two databases, BOSTON and DENVER, and has the same password, HR.
You have the CREATE DATABASE LINK and CREATE SESSION privileges on both the database.
BOSTON is defined as a service name in the tnsnames.ora of both the databases.
You plan to use the command:
CREATE DATABASE LINK hr_link CONNECT to hr IDENTIFIED BY hr USING 'denver'; What must be done to ensure only the HR user in the BOSTON database can access the HR schema in the DENVER database?