When you provision an Oracle Cloud Infrastructure (OCI) Base Database Service on a virtual machine, the system uses OCI Block Volumes for the persistent storage of database files (such as datafiles, control files, and redo logs). These high-performance, network-attached block storage volumes are attached to the compute VM instance that hosts the database. This configuration provides durable, scalable, and reliable storage required for enterprise database workloads. While some specific VM shapes offer local NVMe storage, Block Volumes are the standard and primary storage mechanism for most VM shapes available for the Base Database Service.

B. Object Storage is the default storage option for database datafiles.

Object Storage is designed for unstructured data and is used for backups and archives due to its high latency, not for the high-performance I/O operations of active database datafiles.

C. Local NVMe storage is always the default for BaseDB.

Local NVMe storage is only available on specific high-performance "DenseIO" VM shapes. Standard VM shapes, which are commonly used, rely exclusively on remote Block Volumes for storage.

D. File Storage is mandatory for database backups.

The primary and default destination for managed database backups in the Base Database Service is OCI Object Storage, not File Storage. File Storage is not a mandatory component for backups.

1. Oracle Cloud Infrastructure Documentation, "Overview of Bare Metal and Virtual Machine DB Systems":

Under the section for Virtual Machine DB Systems, it states: "The DB system uses Oracle Cloud Infrastructure Block Volumes for database storage." This directly supports the correct answer (A) and refutes option C's claim that local storage is always the default.

Reference: Oracle Cloud Infrastructure Documentation > Databases > Base Database Service > For Administrators > Overview of Bare Metal and Virtual Machine DB Systems.

2. Oracle Cloud Infrastructure Documentation, "Backing Up a Database on a VM DB System":

This document details the backup options, stating: "The Base Database service supports two backup destinations for DB systems: Oracle Cloud Infrastructure Object Storage...and local storage on the DB system host..." This confirms Object Storage is a primary backup destination, refuting the claims in options B and D.

Reference: Oracle Cloud Infrastructure Documentation > Databases > Base Database Service > For Users > Backing Up and Restoring > Backing Up a Database on a VM DB System.

3. Oracle Cloud Infrastructure Documentation, "Storage Options for Your DB System":

This page clarifies the storage types: "Virtual machine DB systems can use Oracle Cloud Infrastructure Block Volumes storage or local NVMe storage." It further explains that Block Volumes are used for standard shapes, while local NVMe is for DenseIO shapes, invalidating the "always" in option C.

Reference: Oracle Cloud Infrastructure Documentation > Databases > Base Database Service > For Administrators > DB System Storage.