NEVER Do This
NEVER terminate instances without --preserve-boot-volume false
# DEFAULT OCI behavior: boot volume PRESERVED after instance termination
oci compute instance terminate --instance-id <ocid> --force
# Instance gone, but boot volume keeps charging at $0.025/GB/month FOREVER
# RIGHT: explicitly delete boot volume
oci compute instance terminate \
--instance-id <ocid> \
--preserve-boot-volume false
resource "oci_core_instance" "dev" { preserve_boot_volume = false }
20 forgotten boot volumes at 50GB = $25/month = $300/year
**NEVER leave reserved public IPs unattached**
Reserved IP: $0.01/hour = $7.30/month (charged whether attached or not) Ephemeral IP: $0 (auto-deleted when instance terminated)
Use RESERVED only when you need a static IP that survives instance termination. Use EPHEMERAL for everything else.
5 forgotten reserved IPs = $36.50/month = $438/year Detection: oci network public-ip list --scope REGION --lifetime RESERVED
**NEVER assume stopped resources = zero cost**
Stopped Compute Instance: Compute: $0 (stopped) Boot volume: $0.025/GB/month CONTINUES Block volumes: $0.025/GB/month CONTINUES Reserved IP (if attached): $7.30/month CONTINUES
Stopped Autonomous Database: Compute: $0 (stopped) Storage: $0.025/GB/month CONTINUES Backups: Retention charges CONTINUE
Rule: Stopped = compute paused, storage still charged. For long-term idle (>30 days): terminate + backup, restore when needed.
**NEVER send large data via internet egress without calculating cost first**
OCI egress pricing: First 10 TB/month: FREE 10-50 TB: $0.0085/GB 50+ TB: contact sales
15 TB bulk export = 5 TB chargeable × $0.0085/GB × 1024 = $43,520
Cheaper alternatives:
- OCI FastConnect (1 Gbps): $1,100/month flat, breakeven at 130 GB/month
- Intra-region transfer between OCI services: FREE
- Cross-region transfer (OCI to OCI): FREE (intra-Oracle network)
**NEVER over-commit Universal Credits without understanding non-transferability**
Credits are NON-TRANSFERABLE between service categories: Compute credits → compute only Database credits → database only Cannot move surplus to another category
Commit $10k/month compute, use $6k → $4k/month waste ($48k/year). Monthly credits EXPIRE end of month (no rollover = use-it-or-lose-it).
RIGHT: Analyze 6 months historical usage per category. Commit to 70-80% of baseline, not peak.
**NEVER rely on FORECAST budget alerts as your primary alert**
OCI FORECAST uses simple linear projection (30-40% error rate). Week 1 includes one-time data migration → forecast projects 4× that for month.
RIGHT: Set ACTUAL spend alerts at 50%, 75%, 90%, 100%. Use FORECAST for trend awareness only, not budget enforcement. Budgets are ALERTING only — cannot block spending.
**NEVER use NAT Gateway for high-traffic applications**
NAT Gateway cost: $0.01/hr ($7.30/month) + $0.01/GB processed 5 TB/month outbound: $7.30 + (5000 × $0.01) = $57.30/month
Alternative: Ephemeral public IP on instance Cost for <10 TB egress: $0/month
NAT Gateway makes sense for:
- Private subnets with <100 GB/month egress
- Security requirement (no public IPs on instances)
---
## Shape Migration Savings
**Fixed → Flex (right-size RAM separately from OCPU):**
VM.Standard2.4: 4 OCPU, 60 GB RAM (fixed 1:15 ratio) Cost: $0.24/hr = $175/month
VM.Standard.E4.Flex: 4 OCPU, 16 GB RAM (custom ratio) Cost: ($0.02/OCPU × 4) + ($0.0015/GB × 16) = $0.104/hr = $76/month
Savings: $99/month per instance (56% reduction)
**AMD → Arm (50% compute cost reduction):**
VM.Standard.E4.Flex: 4 OCPU, 16 GB RAM → $58.40/month VM.Standard.A1.Flex: 4 OCPU, 16 GB RAM → $29.20/month Savings: $29.20/month (50% reduction)
Gotcha: ARM64 architecture — verify Docker images, compiled binaries, and language runtimes support arm64 before migrating.
---
## Free Tier Maximization
Always-Free tier if fully utilized saves ~$727/month ($8,730/year):
Compute: 2× AMD Micro VMs: $14/month 4 Arm OCPU (24 GB): $29.20/month
Database: 2× Autonomous Databases: $584/month (2 ECPU each, 20 GB storage)
Storage: 200 GB block + 10 GB object + 10 GB archive: $5.28/month
Networking: 1 load balancer + 10 TB egress: $95/month
**Critical gotcha**: 2 ADB limit is TENANCY-wide (not per region, not per compartment). Counted across all regions.
---
## Storage Lifecycle Optimization
10 TB compliance data, accessed quarterly:
Without tiering (Standard all year): 10,000 GB × $0.0255/GB/month × 12 = $3,060/year
With lifecycle rule (Archive after 30 days): Month 1 (Standard): $255 Months 2-12 (Archive): 10,000 GB × $0.0024 × 11 = $264 Total: $519/year
Savings: $2,541/year (83% reduction) Retrieval cost: $0.01/GB — acceptable for quarterly access
Lifecycle policy: Day 0-30 Standard → Day 31+ Archive.
---
## Dev/Test Auto-Shutdown Savings
10 dev instances, 2 OCPU each: 24/7: 10 × 2 × $0.02/hr × 730 = $292/month
Weekdays 9am-6pm only (195 hours/month): 10 × 2 × $0.02 × 195 = $78/month
Savings: $214/month (73% reduction)
Implementation: Tag instances: Environment=Development OCI Functions for start/stop OCI Scheduler: Start weekdays 9am, Stop weekdays 6pm
---
## Hidden Cost Detection (Monthly Audit)
```bash
# 1. Orphaned boot volumes (most common waste)
oci bv boot-volume list --all --lifecycle-state AVAILABLE \
| jq '.data[] | select(."attached-instance-id" == null)'
# 2. Unattached block volumes
oci bv volume list --all --lifecycle-state AVAILABLE
# 3. Reserved IPs without attachment
oci network public-ip list --scope REGION --lifetime RESERVED \
| jq '.data[] | select(."assigned-entity-id" == null)'
# 4. Stopped instances still paying for volumes
oci compute instance list --lifecycle-state STOPPED
# 5. Old backups (filter by date)
oci bv backup list --all \
| jq '.data[] | select(.["time-created"] < "2025-01-01")'
# 6. Load balancers with no backends
oci lb load-balancer list --all
# 7. Object Storage buckets that may be empty
oci os bucket list --all --fields approximateCount,approximateSize
Reference Files
Load references/oci-cost-cli.md when:
- Setting up budgets and multi-threshold alert rules
- Querying usage reports via CLI (
oci usage-api) - Managing service limits and quotas
- Downloading detailed cost and usage reports