Providing su access to group of users in Oracle Cloud.
Add below line in /etc/sudoers.d/90-cloud-init-users
%dba ALL=(ALL) NOPASSWD: /bin/su – oracloud
And then restart ssh daemon services
#/sbin/service sshd restart
Dba – group
ALL – all hosts
(ALL) – All users
NOPASSWD: – no password