It´s a limit in SQL*PLUS, from the manuals :

"ORA-01704 string literal too long

Cause: A quoted string specified as a constant was too long.

Action: Quoted strings may not contain more than 2000
characters."

You must to break the string, something like :

insert xxx values ('string < 2000 chars' || 'another piece of the string ' || 'another' ......


Regards,

Chiappa