Availability Domain-Specific Resources
DB Systems
ephemeral public IPs
instances: They can be attached only to volumes in the same availability domain.
subnets: When you create a subnet, you choose whether it is regional or specific to an availability domain. Oracle recommends using regional subnets.
volumes: They can be attached only to an instance in the same availability domain.

Explanation
References: https://docs.cloud.oracle.com/iaas/Content/Database/Tasks/launchingDB.htm

You can copy objects to other buckets in the same region and to buckets in other regions.
You must have the required access to both the source and destination buckets when performing an object copy. You must also have permissions to manage objects in the source and destination buckets.
Because Object Storage is a regional service, you must authorize the Object Storage service for each region carrying out copy operations on your behalf. For example, you might authorize the Object Storage service in region US East (Ashburn) to manage objects on your behalf. Once you authorize the Object Storage service, you can copy an object stored in a US East (Ashburn) bucket to a bucket in another region.
You can use overwrite rules to control the copying of objects based on their entity tag (ETag) values.
Specify an existing target bucket for the copy request. The copy operation does not automatically create buckets.