In this case, I guess to discovered the problem and the solution
The real problem is the number of cursors that are opened in the Oracle 11g server to perform queries from the Oracle server 12c when it comes to make exportation data.
The solution then is to increase the maximum number of cursors that can be open on the server Oracle 11g through the sentence:
alter system set open_cursors = 1000 scope = both;
To monitor open cursors, query v$sesstat where name='opened cursors current'. This will give the number of currently opened cursors, by session:
--total cursors open, by session
select a.value, s.username, s.sid, s.serial#
from v$sesstat a, v$statname b, v$session s
where a.statistic# = b.statistic# and s.sid=a.sid and b.name = 'opened cursors current';
I hope this will help other people.