If you think a boot volume issue is causing a compute instance problem, you can stop the instance and detach the boot volume using the steps described in this topic. Then you can attach it to another instance as a data volume to troubleshoot it.
Required IAM Policy
To use Oracle Cloud Infrastructure, you must be granted security access in a policy by an administrator. This access is required whether you're using the Console or the REST API with an SDK, CLI, or other tool. If you get a message that you don't have permission or are unauthorized, verify with your administrator what type of access you have and which compartment to work in.
You can detach a boot volume from an instance only when the instance is stopped. See Stopping, Starting, or Restarting an Instance for information about managing an instance's state.
Open the navigation menu and click Compute. Under Compute, click Instances.
Choose your Compartment.
Click the instance that you want to detach the boot volume from.
Under Resources, click Boot Volume.
Click the Actions menu () for the boot volume, and then click Detach Boot Volume. Confirm when prompted.