Automatic DB system version upgrades in OCI are performed to the next release in sequence. This means that the system is upgraded to the next available version rather than skipping to the most recent release, ensuring a stable and tested upgrade path.

When creating a channel for replication in MySQL, the following must be provided:
* Channel name(Answer A): The unique identifier for the replication channel.
* Source connection SSL mode(Answer B): Specifies the SSL mode for the connection to the source server.
* Source connection password(Answer D): The password for the source server connection.
Steps:
* UseCHANGE MASTER TOcommand to set up the replication channel.
* Provide the channel name, SSL mode, and connection password as part of the configuration.
References:
* MySQL Replication Documentation
* Setting Up Replication Channels

B:ENGINE=csv SECONDARY_ENGINE=lakehouse ENGINE_ATTRIBUTE='{"file": [{"region":
"us-ashburn-1", "namespace": "mytenant", "bucket": "bucket01", "name": "airport.csv"}] }': This table option defines a Lakehouse external table based on a CSV file. It specifies thecsvengine for the table and uses thelakehouseas the secondary engine, along with the file's location details in OCI Object Storage.

To deploy a high-availability MySQL DB system in a region with multiple availability domains, the following types of subnets provide maximum redundancy:
* A private regional subnet(Answer B): This type of subnet spans all availability domains in the region, ensuring high availability and fault tolerance.
* A public regional subnet(Answer C): Similar to the private regional subnet, a public regional subnet spans all availability domains, providing maximum redundancy and accessibility.
References:
* OCI Networking Documentation
* MySQL High Availability Documentation

To change the configuration of a high-availability DB system, you must follow these steps:
* Stop the DB system: This ensures that the system is in a consistent state and that no transactions are being processed during the configuration change.
* Edit the DB system: Make the necessary changes to the configuration.
* Change the configuration: Apply the configuration changes.
* Start the DB system: Restart the system to apply the new configuration settings.