can you try to drop and recreate the database links after making sure parameter compatible is set to the current
version and also that parameter sec_case_sensitive_logon = TRUE ?
The old version passwords were likely found with a sql similar to this one:
select name, host, userid from sys.link$ where PASSWORDX like '05%';
Harm ten Napel
Thanks a lot Harm,
Actions "drop and recreate the database links" have solved my issue.