Unable to Change OPERATIONS user Password

Hello Everyone,

We want to change password of OPERATIONS user for security reasons. I tried to do it three ways but not working. Please guide me to resolve the issue.

1. System Administrator > Security > Users

    Password field is not enabled so can not change password from there.

2. FNDCPASS utility

    After executing FNDCPASS command gettng error " This password is not managed by Oracle Application so it cannot be changed from here"

3. Executed API fnd_user_pkg.ChangePassword

    After executing API got error "ORA-0000: normal, successful completion"

EBS: 12.1.3

OS: Linux

Please guide to get out of this issue as soon as possible.

Thanks,