How does one copy data from one database to another in SQL*Plus?

The SQL*Plus COPY command is one of the fastest ways of copying data between databases and schemas. This is also one of the few methods that will handle LONG columns correctly. Look at this example:

SQL> COPY FROM scott/tiger@db1 TO scott/tiger@db2 INSERT mytable USING select * from mytable;

COPY
----

Copies data from a query to a table in the same or another
database. COPY supports CHAR, DATE, LONG, NUMBER and VARCHAR2.

COPY {FROM database | TO database | FROM database TO database}
           {APPEND|CREATE|INSERT|REPLACE} destination_table
           [(column, column, column, ...)] USING query

where database has the following syntax:
    username[/password]@connect_identifier

Note that this command is no more enhanced since Oracle 8.0 and may be declared as obsolete in a future version (but is still there in 11gR2) but there is no replacement to easily copy tables with LONG column (LONG datatype is obsolete).