Why is SQL*Plus' desc table not showing not null constraints after using dbms_redefinition
This is a known bug (description is not public unfortunately):

Bug:4396234 ET10.2OREDEF: NULLABLE COL OF *_TAB_COLUMNS TABLE NOT UPDATED AFTER ONLINE REDEF

The NOT NULL constraints are copied as NOVALIDATE, and you have to set them to VALIDATE state manually, e.g:

ALTER TABLE t84_redefenition ENABLE VALIDATE CONSTRAINT constraint_name;


The primary key issue is similar, but there is no bug reported for that. However I have found that disabling and reenabling it solves the problem.

ALTER TABLE t84_redefinition DISABLE PRIMARY KEY;
ALTER TABLE t84_redefinition ENABLE PRIMARY KEY;