https://blogs.oracle.com/developers/deploy-containers-on-oracle-container-engine-for-kubernetes-using-developer-cloud

https://docs.oracle.com/en/cloud/paas/app-builder-cloud/csapb/staging-and-publishing-application.html#GUID-4FAD8622-4A32-46EC-92FE-074E557580CA he live application is visible to users according to the Login Security settings for the application.
Each time that you are ready to publish a new version of your application you should lock the live version of your application until the new version is published. This prevents any changes being made to the database that could be lost during the process. While the application is locked you can import the live data into the staging database, if necessary. You can unlock the application after the new version is published.
You cannot make changes to a version of an application after it is published and live. To make additional changes to the application you need to create a new version.
* Publishing an Application
* Managing Data During the Development Lifecycle
* Creating a New Version of an Application

https://docs.cloud.oracle.com/en-us/iaas/Content/ContEng/Tasks/contengmodifyingcluster.htm

Failed to validate DB connectivity
When you create a domain that includes the Java Required Files (JRF) components, you must select an existing database and provide connection details. The compute instances use this information to connect to the database and provision the JRF database schemas.
Possible causes for this error include:
* You entered the wrong database password or a plain text password.
* The database does not allow the compute instances to access its listen port (1521 by default).
* Oracle Autonomous Transaction Processing - Check your access control list (ACL).
* Oracle Cloud Infrastructure Database - Check the network security group that was assigned to the database, and the security lists for the subnet on which the database was created.
* You selected an Oracle Cloud Infrastructure Database running Oracle Database 12c or later, and you did not provide the name of a pluggable database (PDB).
https://docs.oracle.com/en/cloud/paas/weblogic-cloud/user/troubleshoot-oracle-weblogic-cloud.html#GUID-61D816F9-CD69-475A-A7C9-66A00752FBB2