1. Why OCI Free Tier?

OCI's free tier offers the largest resource allocation in the industry with no time limit. Compared to equivalent AWS and GCP free tiers, the difference is stark.

Item OCI Always Free AWS Free Tier (12 months) GCP Always Free
Core VM ARM Ampere A1 4 OCPU / 24 GB RAM t2.micro / t3.micro 1 vCPU / 1 GB RAM e2-micro 1 vCPU / 1 GB RAM
Instance splitting Up to 4 instances 1 instance 1 instance
Additional x86 E2.1.Micro 2 instances (1 OCPU / 1 GB) — —
Block storage 200 GB 30 GB EBS 30 GB
Outbound traffic 10 TB/month 100 GB/month 1 GB/month
Duration Unlimited (Always Free) 12 months Unlimited

The key isn't just ARM 4-core 24GB hardware — it's that this is free forever. It's effectively the only free cloud capable of running real workloads: personal VPNs, self-hosted AI agents, K3s clusters, lightweight LLM inference servers.

2. Two Free Tier Tracks

Signing up provides two types of free resources simultaneously. Confusing them can result in charges.

Type Always Free Free Trial
Duration Unlimited 30 days from signup
Limits Fixed resource list (see §3) $300 USD credit
After expiry Continues as-is Unused credit expires; only Always Free remains
Risk Nearly none Creating paid resources within 30 days can auto-bill after credit exhaustion

Principle: If you don't want to be charged, only create resources labeled "Always Free Eligible" in the console for the first 30 days. After 30 days, paid resource creation is blocked (if staying on Always Free).

3. Always Free Resource Details

All limits below apply only within your chosen Home Region.

3.1 Compute

Shape Quantity Specs Notes
VM.Standard.A1.Flex (ARM Ampere) Up to 4 Total 4 OCPU / 24 GB RAM 3,000 OCPU hours + 18,000 GB hours monthly. 4 OCPU x 24h x 31d = 2,976h, well within limits
VM.Standard.E2.1.Micro (AMD x86) 2 Each 1 OCPU / 1 GB RAM For software incompatible with ARM

Mix ARM and x86 for up to 6 concurrent instances. Total boot volumes must not exceed 200 GB.

3.2 Storage

Type Limit
Block Volume (boot + additional) 200 GB total, max 5 volumes
Block Volume Backup 5 (stored in Object Storage)
Object Storage Standard 10 GB + Infrequent Access 10 GB + Archive 10 GB, 50,000 API requests/month (S3 compatible)

3.3 Database

Type Limit
Autonomous Database (ATP/ADW/JSON) 2 instances, each 1 OCPU / 20 GB
NoSQL Database Phoenix region only

3.4 Networking & Other

  • Flexible Load Balancer: 1 (10 Mbps)
  • Network Load Balancer: 1
  • VCN, Site-to-Site VPN: Unlimited
  • Outbound traffic: 10 TB/month
  • Vault, Bastions, Monitoring, Logging: Basic usage free
  • Email Delivery: 200/day

4. Sign-Up Process (Korean Users)

4.1 Prerequisites

Item Recommendation
Card Newly issued VISA/Master credit or debit card
Not accepted PIN debit, prepaid cards, virtual cards, disposable cards (Oracle explicitly rejects)
Email Address never used for OCI Free Tier or previous Free Trial
Phone Number never used for OCI (SMS verification required)
Address (English) Accurate romanized street address (masking/modifying causes rejection)

OCI identifies duplicate signups by email + phone + card number combination. A card can be reused a limited number of times, but using a new card is safer. Most importantly, match the address exactly as registered with your card issuer.

4.2 Steps

  1. Go to https://www.oracle.com/cloud/free/ -> "Start for free"
  2. Email verification -> Set password
  3. Account info: Name must match cardholder name; address in accurate English
  4. Choose Home Region: Once selected, cannot be changed. Korean users typically choose:
    • Seoul (ap-seoul-1): Lowest latency, but ARM capacity frequently full
    • Chuncheon (ap-chuncheon-1): Korea's second region, relatively more capacity
    • Tokyo / Osaka: 30-50ms latency, easier ARM capacity
    • For availability: Chuncheon or Osaka; for latency: Seoul
  5. Phone verification: 010-1234-5678 -> enter 1012345678 (drop leading 0)
  6. Card registration: $1 authorization hold that is immediately reversed. No actual charge
  7. Accept terms -> "Complete Sign-up"

4.3 If Sign-Up Fails

"Transaction processing error" is the most common message. Causes are usually:

  • Card declined (many Korea-issued cards rejected)
  • IP/location mismatch (turn off VPN)
  • Repeated retries with same email/phone/card -> blocked
  • Address doesn't match card registration address

Resolution order:

  1. Retry immediately with a different card (don't repeat with same info)
  2. Contact Oracle Cloud Customer Service chat or form
  3. If still failing, sign up with new email + new phone + new card combination
  4. Facebook "Oracle Cloud KR User Group" has active Oracle Korea employees who can help with rejections

5. ARM Instance Creation: "Out of host capacity" Workaround

The biggest real-world pitfall of OCI Free Tier. Korean and Tokyo regions are almost always at full ARM A1 allocation.

5.1 Recommended Settings

Item Recommendation
Image Canonical Ubuntu 24.04 Minimal aarch64
Shape VM.Standard.A1.Flex
OCPU/RAM 2 OCPU / 12 GB (easier to get than 4 OCPU)
Boot Volume 47-50 GB (default)
SSH Key Local ~/.ssh/id_ed25519.pub or console key pair (download private key immediately)
Public IP Check "Assign a public IPv4 address"

5.2 Capacity Acquisition Strategies (by effectiveness)

  1. Reduce OCPU from 4 to 2: 4 OCPU requests almost always fail. Split into 2 instances at 2 OCPU each — same total resources, much higher success rate.
  2. Try at dawn (KST 02:00-06:00): Resource reclamation occurs during low-activity hours.
  3. Change Availability Domain: Try AD-1, AD-2, AD-3 separately. Capacity varies by AD within the same region.
  4. Auto-retry scripts: OSS like hitrov/oci-arm-host-capacity on GitHub polls the OCI API and creates instances the moment capacity opens up. Requires your OCI API key.
  5. Switch to PAYG: Numerous reports that switching to pay-as-you-go raises ARM capacity priority. Still $0 within Always Free limits, but accidentally creating paid resources will incur charges — set console alerts for unused paid services.

5.3 If Still Can't Get One

  • Create a VM.Standard.E2.1.Micro (AMD) instance first. Instantly created. Try ARM later.
  • To change Home Region, you must create a new account. Already-signed-up accounts can't change their Home Region.

6. Basic Security & Operations Setup

6.1 Networking

OCI blocks all inbound traffic by default. Unlike AWS Security Groups, two layers must be opened:

  1. VCN Security List: Console -> Networking -> Virtual Cloud Networks -> select VCN -> Security Lists -> Default Security List -> Ingress Rules: add 80/443/needed ports
  2. Instance OS iptables: Ubuntu images have iptables enabled for additional blocking. Check and open:
sudo iptables -L INPUT -n --line-numbers
sudo iptables -I INPUT 6 -m state --state NEW -p tcp --dport 80 -j ACCEPT
sudo iptables -I INPUT 6 -m state --state NEW -p tcp --dport 443 -j ACCEPT
sudo netfilter-persistent save

Both steps must be completed or external access won't work.

6.2 SSH Access

ssh -i ~/.ssh/id_ed25519 ubuntu@<public-ip>
# Oracle Linux images use opc instead of ubuntu

6.3 Avoiding Idle Reclamation

Always Free instances are reclaimed when:

  • 7-day CPU 95th percentile below 20% AND
  • 7-day network usage 95th percentile below 20% AND
  • 7-day memory usage 95th percentile below 20%

All three must be simultaneously true, so typical self-hosted workloads (blogs, VPNs, bots) are safe. For truly idle learning VMs, generate artificial load:

# /etc/cron.d/keepalive — 1 minute of CPU load every hour
0 * * * * root timeout 60 yes > /dev/null

6.4 Billing Alert Setup (Essential)

Console -> Billing -> Budgets: create a $1 limit budget. Set email alerts at 50%, 80%, 100% thresholds. Especially important when on PAYG.

7. Common Korean User Pitfalls

Pitfall Consequence Avoidance
VPN on during signup Location mismatch -> rejection Turn off VPN for signup, re-enable after
Prepaid/virtual card Rejection Use VISA/Master credit or debit
Repeated retries with same info Possible permanent block Switch info after 1-2 tries
Requesting 4 OCPU at once Infinite "out of capacity" Split into 2 OCPU x 2 instances
Only opening Security List, not iptables External access blocked Configure both
Docker containers with crypto miners Immediate permanent account ban Only use trusted images; verify even from official hub
Creating paid resources during 30-day trial Auto-billing after $300 credit exhaustion Only use "Always Free Eligible" labeled resources
Wrong Home Region choice Cannot change; need new account Recommend Chuncheon/Osaka

8. Recommended Use Cases

Real workloads possible on ARM 4 OCPU / 24 GB:

Use Configuration Notes
Personal VPN WireGuard alone 1 OCPU sufficient, 10 TB traffic
Blog/Homepage Nginx + WordPress + MariaDB 1 OCPU / 6 GB
K3s Cluster 1 control plane + 3 workers (1 OCPU / 6 GB each) Kubernetes learning
Self-hosted AI Ollama + 7B/8B quantized models 8-20 tokens/s, full 4 OCPU
Automation Workflow n8n + Postgres (Docker Compose) Verify ARM-compatible images
Game Server Minecraft Java + GeyserMC 2 OCPU / 12 GB recommended
Personal DNS/Ad Block AdGuard Home / Pi-hole Almost no resources

ARM compatibility: Most OSS provides multi-arch images. However, some proprietary or old Docker images are amd64-only — check platform options on docker pull. As a last resort, run on E2.1.Micro x86 instances.

9. PAYG (Pay-As-You-Go) Conversion Considerations

Benefits:

  • Easier ARM A1 capacity acquisition
  • Access to paid services (AI/ML, high-performance networking)
  • Official customer support case registration
  • Always Free resources remain free

Risks:

  • Accidentally creating non-"Always Free Eligible" resources incurs immediate charges
  • Boot volume exceeding 200 GB incurs overage charges
  • Traffic exceeding 10 TB incurs overage charges

Decision criterion: Only convert if you absolutely need ARM instances in Korea/Tokyo regions and automated scripts still can't secure them. Otherwise, stay on Always Free.

10. Reference Links

This document assumes Always Free limits only. Paid resource usage requires separate evaluation.