Core Oracle Cloud Infrastructure Services (Compute, Storage, Networking)
Compute
Compute offers virtual machines, bare metal servers and dedicated hosts, in shapes: standard (general purpose), dense I/O, GPU and HPC. Flexible shapes let you choose OCPUs and memory independently. On x86, one OCPU equals one physical core, delivered as two hardware threads (roughly two vCPUs); on Ampere A1 (Arm), one OCPU equals one core. Instances can be stopped without losing the boot volume, and terminated with or without preserving it. Instance configurations and instance pools enable autoscaling.
Storage
Object Storage is a flat, internet-accessible namespace of buckets for unstructured data, with storage tiers, versioning, lifecycle policies, auto-tiering and pre-authenticated requests for temporary access. Block Volume is network-attached storage presented to a single instance at a time and can be detached and reattached or replicated; performance tiers range from lower cost to ultra high performance. File Storage provides shared NFS. Trap: you cannot mount an Object Storage bucket as an ordinary filesystem on a compute instance.
Networking
A Virtual Cloud Network (VCN) is a private network with CIDR blocks; subnets may be regional or AD-specific. Gateways: Internet Gateway (bidirectional internet), NAT Gateway (outbound only, no inbound), Service Gateway (private access to OCI services), Dynamic Routing Gateway (on-premises or other VCNs) and Local Peering Gateway. Security lists apply at the subnet level; network security groups apply at the VNIC level. Route tables decide where traffic goes.
Rule of thumb
A subnet is public only if its route table sends 0.0.0.0/0 to an Internet Gateway. For a private subnet whose hosts need patching, use a NAT Gateway outbound plus a Service Gateway for OCI services - never assign public IPs.