You can use DBaaS Monitor to change the password of the TDE keystore.
When the database deployment is created on Database Cloud Service, a local autologin software keystore is created. The keystore is local to the compute node and is protected by a system-generated password. The keystore is part of the key-based architecture that is used to transparently encrypt (and decrypt) tablespaces.
This feature is only available on database deployments using Oracle Database 12c or later.
To change the TDE keystore password:
On the DBaaS Monitor home page, click Database Status. Or, in the Database pulldown menu, click Manage.
In the menu for your database, click Change TDE Keystore Password.
In the Change TDE Keystore Password dialog box, enter the current keystore password and the new keystore password.
Click OK on the confirmation message.