The easiest way to access from an Oracle database to objects of another Oracle database is using a DBLink (this does not mean that it is always the most desirable, abuse of DBLinks can generate both performance as security problems).
First, you need a user who holds the create database link privilege. Then, you can create DBLink in source database (A) through this simple sentence:
- 'lnk_from_A_a_B ' is the link name,
- 'user' and 'password' are the user identifiers who will use the link to connect.
- 'B' is the SID of the target database.
Through this DBLink you can connect with objects in the remote database with privileges owned by the user of the creation sentence.
To reference an object of the remote database should indicate object name concatenated with '@' and the DBLink name.
Example: select * from mytable@lnk_from_A_a_B