Hard to tell from just ORA-1466. Please paste the entire error from the alert log along with the corresponding trace file, at least the top portion which shows what the process was executing.
There is a few notes on MOS:
ORA-1466 After Upgrade To 22.214.171.124 (Doc ID 1571229.1)
ORA-1466: UNABLE TO READ DATA - TABLE DEFINITION HAS CHANGED (Doc ID 1557739.1)
The cause depends on what the process was doing which we cannot tell with the information provided.