What are logical databases? What are the advantages/disadvantages of logical databases?

To read data from a database tables we use logical database.
A logical database provides read-only access to a group of related tables to an ABAP/4 program.

adv:-
The programmer need not worry about the primary key for each table. Because Logical database knows how the different tables relate to each other, and can issue the SELECT command with proper where clause to retrieve the data.

i)An easy-to-use standard user interface.

ii)check functions which check that user input is complete, correct,and plausible.

iii)meaningful data selection.

iv)central authorization checks for database accesses.

v)good read access performance while retaining the hierarchical data view determined by the application logic.

disadv:-
i)If you don’t specify a logical database in the program attributes, the GET events never occur.

ii) There is no ENDGET command, so the code block associated with an event ends with the next event
statement (such as another GET or an END-OF-SELECTION).