A Compute Classic instance is a virtual machine running a specific operating system and with CPU and memory resources that you specify.
An instance is defined by its machine image and shape. A machine image is a template of a virtual hard disk that has a specific operating system installed. See Managing Machine Images. A shape defines the number of CPUs and RAM available to an instance. See About Shapes.
You can specify a name as well as a label to identify your instance. The instance name that you specify becomes a prefix for an ID that’s generated automatically. If you’ve specified a label, then the label is displayed in the web console. Otherwise, the system-generated ID is displayed.
You can assign tags to your instances to make it easy to sort and find instances.
You can attach up to 20 TB of block storage to each of your instances for storing data and applications, by creating multiple persistent storage volumes and attaching them to the instances. Even after you delete instances, the data stored in the storage volumes remains intact until you delete the volumes.
Instances boot from a persistent disk, ensuring that any changes that you make at the operating system-level persist when the instance is re-created.
Configuring Network Settings
You can implement fine-grained control over network access to your instances, both from other Compute Classic instances as well as from external hosts.
When you create an instance, by default, it doesn’t allow access from any other instance or external host. To enable unrestricted communication among some of your instances, you can create a security list and add all the instances to that security list. When you add an instance to a security list, the instance can communicate with all the other instances in the same list.
By default, the instances in a security list are isolated from hosts outside the list. You can override this default setting by creating security rules. Each security rule defines a specific communication path, which consists of a source, a destination, and a protocol-port combination over which communication is allowed.
You can also add your instance to IP networks that you’ve created. An IP network allows you to define an IP subnet in your account. The address range of the IP network is determined by the IP address prefix that you specify while creating the IP network. These IP addresses aren’t part of the common pool of Oracle-provided IP addresses used by the shared network. When you add an instance to an IP network, the instance is assigned an IP address in that subnet. You can assign IP addresses to instances either statically or dynamically, depending on your business needs. So you have complete control over the IP addresses assigned to your instances.