ORA-12660: Encryption or crypto-checksumming parameters incompatible

Error

C:\Users\Oracle>sqlplus hr@xepdb1
SQL*Plus: Release 12.1.0.2.0 Production on Thu May 21 13:00:51 2020
Copyright (c) 1982, 2014, Oracle. All rights reserved.
Enter password:
ERROR:
ORA-12660: Encryption or crypto-checksumming parameters incompatible


Cause:
Parameter defined at Client side SQLNET file is wrong.

At Server parameter SQLNET file:
sqlnet.encryption_server = REQUIRED
sqlnet.encryption_types_server = (AES256)

At Client Parameter SQLNET file:
SQLNET.ENCRYPTION_CLIENT=REJECTED
SQLNET.ENCRYPTION_TYPES_CLIENT=(AES256)


Solution
We need to modified the client side SQLNET.ora file and change the parameter ENCRYPTION_CLIENT as per our requirement.

Following are the parameter value:
ACCEPTED : Allow both encrypted and non-encrypted connections.(Default)
REJECTED : Only un-encrypted traffic.
REQUESTED : The client or server will request encrypted traffic if it is possible, but will accept non-encrypted traffic if encryption is not possible.
REQUIRED : Only accept encrypted traffic.

We required encryption, so we modified according to that.

At Client Parameter SQLNET file:
SQLNET.ENCRYPTION_CLIENT=REQUIRED
SQLNET.ENCRYPTION_TYPES_CLIENT=(AES256)