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Wave Migration Sequencer & Rollback Triggers

Migration Sequencer High-Acuity Resilience

1. 5-R Workload Rationalization Engine

When an acquisition is finalized, every discovered server, database, and clinical microservice is classified into one of five rationalization buckets:

graph TD
    App[Discovered Application / Workload] --> Evaluation{Architectural Assessment}

    Evaluation -->|Legacy Monolith / Fixed Vendor Support| Rehost["1. REHOST (Lift & Shift)<br/>Azure Migrate VM Replication"]
    Evaluation -->|Standardized Web/App / Containerizable| Replatform["2. REPLATFORM<br/>Azure App Service / AKS Microservices"]
    Evaluation -->|Monolithic EHR Replacement| Refactor["3. REFACTOR<br/>Migrate to Enterprise Core Epic SaaS/Azure PaaS"]
    Evaluation -->|Medical Modality Hardware Bound| Retain["4. RETAIN<br/>Isolate on Local Clinic Edge VLAN"]
    Evaluation -->|Redundant / Duplicate Capability| Retire["5. RETIRE<br/>Archive Data & Decommission VM"]

2. 4-Phase Wave Execution Sequencer

Workloads migrate in structured waves to eliminate blast radius and ensure emergency department and ICU clinical operations remain uninterrupted.

gantt
    title M&A 90-Day Wave Migration Timeline
    dateFormat  YYYY-MM-DD
    section Phase 0: Foundation
    Transit VNet & NAT Deployment      :done,    p0_1, 2026-09-01, 10d
    Azure Migrate Appliance Install    :done,    p0_2, 2026-09-05, 7d
    EDR Deployment & Sentinel Onboard  :active,  p0_3, 2026-09-08, 8d
    section Phase 1: Corporate Pilot
    Active Directory Sync & O365 Coex  :p1_1, 2026-09-15, 14d
    Corporate ERP & Intranet Migration :p1_2, 2026-09-20, 10d
    section Phase 2: Tier-2 Clinical
    PACS Archive Data Hydration        :p2_1, 2026-09-28, 20d
    Lab & Pharmacy Interface Testing   :p2_2, 2026-10-05, 15d
    section Phase 3: Tier-1 Core EHR
    Epic EHR Delta Sync & Validation   :p3_1, 2026-10-20, 7d
    Go-Live Final Cutover Window (4h)  :milestone, p3_cut, 2026-10-27, 0d
    Decommission Legacy Hardware       :p3_2, 2026-10-28, 14d

Phase Details

  1. Phase 0: Foundation & Network Quarantine (Days 1–15)
  2. Deploy Transit VNet (10.245.0.0/20) with Azure Firewall inspection.
  3. Establish Site-to-Site IPsec VPN to acquired datacenter.
  4. Deploy Azure Migrate Hyper-V / VMware virtual appliance.

  5. Install CrowdStrike / Defender for Endpoint agents on all endpoints.

  6. Phase 1: Pilot & Corporate Systems (Days 16–30)

  7. Synchronize Entra ID identities via Entra Cloud Sync.
  8. Migrate file servers, payroll ERP, and internal intranet portals.

  9. Verify identity federation and Conditional Access enforcement.

  10. Phase 2: Tier-2 Clinical Supporting Systems (Days 31–60)

  11. Pre-seed secondary PACS imaging archives (DICOM studies > 2 years old) to Azure Blob Storage (Cold Tier).

  12. Replatform Lab Information Systems (LIS) and Pharmacy dispensing interfaces to containerized AKS clusters.

  13. Phase 3: Tier-1 EHR Core Cutover (Days 61–90)

  14. Initialize continuous database block-level replication (Azure Site Recovery / Always On Availability Groups).
  15. Execute scheduled 4-hour weekend cutover window during low clinical census.

3. Pre-Flight Go/No-Go Gate Criteria

Prior to commencing any final production cutover, all six pre-flight criteria must be certified by the Incident Commander:

[ ] 1. Data Replication Lag: < 1.0 seconds across all database replicas.
[ ] 2. Identity Verification: 100% of clinicians authenticated successfully via Entra ID MFA.
[ ] 3. Network Latency: Round-trip time (RTT) from clinic edge to Azure Virtual WAN Hub < 18ms.
[ ] 4. Rollback Snapshots: Immutable SAN snapshot and Azure backup verified.
[ ] 5. ARB Sign-Off: Lead Clinical Informaticist and CISO formal sign-off recorded.
[ ] 6. Help Desk Preparedness: Dedicated high-priority triage queue active with 24/7 staffing.

4. Automated Rollback Triggers & Runbook

If any critical failure threshold is exceeded during the cutover window, the automated rollback trigger is engaged:

flowchart TD
    CutoverStart[Cutover Execution Window Initiated] --> Monitor{Continuous Metric Monitoring}

    Monitor -->|"Condition A: Database Lag > 120s"| EngageRollback[Engage Automated Rollback]
    Monitor -->|"Condition B: Clinical Interface Error Rate > 0.5%"| EngageRollback
    Monitor -->|"Condition C: Network Packet Loss > 2% for 5 mins"| EngageRollback
    Monitor -->|"All Metrics Nominal"| Validate[Clinical Workflow Validation Passed]

    Validate --> Finalize[Commit Cutover & Update DNS Records]

    EngageRollback --> R1[1. Revert BGP Route Announcement to Legacy DC]
    R1 --> R2[2. Power On Source Hypervisors from Quiesced State]
    R2 --> R3[3. Re-enable Legacy HL7 Interface Engines]
    R3 --> R4[4. Notify ARB & Incident Management Channel]

Rollback Metric Thresholds

Trigger Code Metric Monitored Critical Threshold Automated Action
TRG-01 Database Replication Lag > 120 seconds for > 3 minutes Halt cutover; failback to primary on-prem cluster.
TRG-02 HL7 Interface Message Drops > 10 unacknowledged messages Revert MLLP DNS routes to on-prem interface engine.
TRG-03 End-to-End Synthetic Latency RTT > 45ms for > 5 minutes Re-route clinical traffic via backup MPLS circuit.
TRG-04 Clinician Login Failure Rate > 2.0% failed authentications Re-enable legacy AD federation endpoint temporarily.