# OCI Service: Autonomous Database Serverless (ADB-S)
# Last verified: 2026-03

service:
  name: "Autonomous Database Serverless (ADB-S)"
  id: adb_serverless
  category: database
  color: "#AA643B"

features:
  auto_scaling: true
  auto_indexing: true
  auto_tuning: true
  auto_patching: true
  transparent_application_continuity: true
  autonomous_data_guard: true
  private_endpoints: true
  byol_eligible: true

ha_dr_options:
  local_ha: "Built-in TAC (Transparent Application Continuity) — ~0 perceived RTO"
  same_region_adg: "Autonomous Data Guard standby — synchronous, RPO 0"
  cross_region_adg: "Cross-region ADG — asynchronous only, RPO seconds (switchover RPO 0, manual failover RPO up to 1 min), RTO < 10 min"
  cross_region_auto_failover: "NOT available — cross-region requires manual switchover/failover only"

limits:
  max_ecpu: 512
  max_ocpu_legacy: 128
  max_storage_tb: 384
  max_auto_scale: "3x base ECPUs"
  auto_scale_activation: "2-3 minutes"
  min_ecpu: 2
  min_storage_tb: 1
  notes: "ECPU is now the default billing unit. 4 ECPUs ≈ 1 OCPU. OCPU billing is legacy."

variants:
  - id: adb_s
    name: "Autonomous Database Serverless (ADB-S)"
    description: "Shared Exadata infrastructure, fully managed, auto-scaling"
    workload_types:
      - ATP (Transaction Processing / Mixed)
      - ADW (Data Warehouse / Analytics)
      - AJD (JSON Document Store)
      - APEX (Low-code application development)

  - id: adb_d
    name: "Autonomous Database on Dedicated Exadata (ADB-D)"
    description: "Dedicated Exadata infrastructure, full isolation"
    use_when:
      - "Strict isolation requirements (regulatory, multi-tenant)"
      - "Predictable performance with no noisy-neighbor risk"
      - "Need RAC for horizontal compute scaling"
      - "> 128 OCPUs sustained"

when_to_use:
  - "Oracle Database workloads migrating to cloud"
  - "Need automated patching, tuning, and scaling"
  - "BYOL opportunity with existing Oracle DB licenses"
  - "JSON document workloads (AJD)"
  - "Rapid APEX application development"
  - "Data warehouse / analytics with auto-scaling"

when_not_to_use:
  - "Non-Oracle database engines (use MySQL HeatWave, PostgreSQL, NoSQL)"
  - "Need OS-level access or custom DB home configuration → use DBCS"
  - "Need RAC but not ADB-D budget → use ExaCS or DBCS VM"
  - "Workloads requiring specific DB patches not yet in ADB"
  - "Extreme IOPS requirements > what Exadata provides"

sizing:
  adb_s:
    min_ecpu: 2
    max_ecpu: 512
    min_ocpu_legacy: 1
    max_ocpu_legacy: 128
    auto_scaling: "Up to 3x base ECPUs (takes 2-3 minutes to activate)"
    sizing_guidance: "Size base ECPUs for P75 sustained load, not P50. Auto-scaling covers peaks but has activation latency. 4 ECPUs ≈ 1 OCPU."
    storage_min_tb: 1
    storage_max_tb: 384
    iops: "Proportional to OCPU count, Exadata storage servers"

  adb_d:
    min_ocpu: "2 per VM (minimum 2 VMs for HA)"
    max_ocpu: "Per Exadata infrastructure shape"
    rac: true
    storage: "Exadata storage dependent on infrastructure shape"

gotchas:
  - id: adb_s_autoscale_latency
    severity: MEDIUM
    description: "Auto-scaling activation takes 2-3 minutes. Size base OCPUs for P75, not average."

  - id: adb_s_private_endpoint
    severity: HIGH
    description: "Always use private endpoints for production. Public endpoints allow internet access to the DB listener."

  - id: adb_s_service_gateway
    severity: MEDIUM
    description: "ADB-S requires a Service Gateway in the VCN for automated backups to Object Storage."

  - id: adb_s_byol_savings
    severity: LOW
    description: "BYOL pricing is ~50% cheaper than License Included. Always check if customer has existing Oracle DB licenses."

  - id: adb_d_minimum_infra
    severity: HIGH
    description: "ADB-D requires dedicated Exadata infrastructure — minimum cost is significant. Don't recommend for small workloads."

  - id: adb_data_guard_async
    severity: MEDIUM
    description: "Cross-region Autonomous Data Guard is async only (RPO > 0). For zero RPO, need same-region standby or ADB-D with local Data Guard."

  - id: adb_version
    severity: LOW
    description: "ADB now defaults to Oracle 26ai in all commercial regions. 19c is legacy. Verify customer version requirements."

implied_dependencies:
  - service: service_gateway
    reason: "Required for automated backups to Object Storage"
  - service: private_endpoint
    reason: "Production workloads must use private endpoints"
  - service: oci_vault
    reason: "Customer-managed encryption keys (recommended for production)"
  - service: data_safe
    reason: "Security assessment, audit, and data masking"

competitive:
  vs_aws_rds:
    advantages:
      - "Autonomous operations (auto-patching, auto-tuning, auto-scaling)"
      - "Dramatically lower DB licensing cost with BYOL"
      - "Exadata performance for Oracle workloads"
    disadvantages:
      - "No multi-engine support (Oracle only)"
      - "Auto-scaling latency vs. Aurora's faster scale-out"
  vs_azure_sql:
    advantages:
      - "Oracle-native features (RAC, Data Guard, Advanced Compression)"
      - "BYOL cost advantage"
    disadvantages:
      - "Azure has broader SQL Server ecosystem integration"

references:
  documentation: "https://docs.oracle.com/en/cloud/paas/autonomous-database/"
  pricing: "https://www.oracle.com/autonomous-database/pricing/"
  sizing_guide: "https://docs.oracle.com/en/cloud/paas/autonomous-database/adbsa/autonomous-database-cpu.html"

changelog:
  - date: "2026-03-14"
    contributor: { name: "Diego Cabrera", team: "Field Architecture" }
    change: "Initial creation with sizing rules, gotchas, competitive notes, HA/DR options"
