Exporting questionable statistics occurs when Exporting ORACLE databases in Linux. Error Handling

Environment: machine A and machine B are both LINUX systems. However, machine B has insufficient space, so after the database service is stopped, you are ready to export data on machine.
Export Statement exp user/password @ sid file = 0320.dmp
The error Exporting questionable statistics. does not occur during the export process.
The character set is a problem.
Use a statement to view the character set of the database.
Select * from nls_database_parameters t where t. parameter = 'nls _ CHARACTERSET ';
Or
Selct * from v $ nls_parameters where parameter = 'nls _ CHARACTERSET ';
The result is the same. Both devices A and B are ZHS16GBK. Strange. Why not? After looking at the system character set of machine A, I found that it is in simplified Chinese. Will it be the problem?
Use it on machine A again
Export NLS_LANG = AMERICAN_AMERICA.ZHS16GBK
If you export data again, there will be no errors.
It turns out that the character set of the system is incorrect, rather than that of ORACLE.