#009 MIGRATE Mainframe application to Azure Cloud
1 yr plan Month by Month
FIRST will describe 3 migration approaches and then breakdown the Cloud Migration as a 1 yr plan with cost each month
1. Three Migration Approaches to Azure Cloud
A) Rehost (Lift & Shift)
➡️ Move workloads as-is:
IBM i → Skytap on Azure (runs IBM i LPARs)
z/OS → OpenText Micro Focus Enterprise Server / TmaxSoft OpenFrame on Azure VMs
Pros:
Fastest path to leave on-prem data center.
Minimal code change (keep COBOL, RPG, JCL).
Ops consolidated under Azure (networking, monitoring, backup).
Cons:
Still carries legacy technical debt.
Licensing cost (Skytap, Micro Focus, etc.).
Not cloud-native (limited autoscale, modern DevOps).
B) Replatform (Modernize selected layers)
➡️ Keep core business logic (COBOL/RPG), but:
Expose via APIs (z/OS Connect, IBM i Web Services)
Migrate Db2 → Azure SQL Managed Instance
New services → App Service / AKS
Pros:
Reduce infra/DB cost with Azure SQL.
Step toward cloud-native while preserving proven logic.
Easier to hire skills for Azure services vs. mainframe admins.
Cons:
Requires integration testing & schema conversions.
Dual-write/CDC complexity during cutover.
Moderate project effort (not as fast as rehost).
C) Refactor (Rebuild in Cloud-native)
➡️ Rewrite COBOL/RPG business logic in Java/.NET microservices on AKS/App Service, event-driven with Service Bus/Event Hubs, Db2 fully migrated to Azure SQL.
Pros:
Full agility: cloud-native, DevOps, CI/CD.
Autoscaling and lower long-term TCO.
Larger talent pool (Java/.NET engineers).
Cons:
Highest cost and time upfront.
Regression risk (rewriting proven code).
Needs extensive test harnesses & domain experts.
2. Selected Approach for Plan → Replatform
(Reason: Balanced — not just a lift-and-shift, but not as risky as full refactor. Keeps business logic intact while modernizing DB + APIs + integration.)
3. 12-Month Month-by-Month Plan (Replatform)
M1 — Discovery & Strategy
Inventory all apps, batch jobs, DB schemas.
Define target Azure architecture (hub-spoke VNet, Key Vault, Monitor).
Pick migration tooling (Azure Data Factory, DMS, API Mgmt).
M2 — Landing Zone & Connectivity
Build Azure landing zone with RBAC, policies.
Set up ExpressRoute/VPN.
Enable logging/monitoring (Log Analytics, App Insights).
M3 — Data Assessment
Run SSMA (SQL Server Migration Assistant) on Db2 schemas.
Prototype schema conversion.
Identify datatype/function gaps.
M4 — API Wrappers for Legacy
Expose CICS transactions with z/OS Connect.
Expose RPG services with IBM i IWS/Node.js.
Publish in API Management.
M5 — Bulk Data Migration (Pilot)
Create Azure SQL MI.
Use ADF/DMS for PRODUCT & CUSTOMER tables.
Validate row counts, integrity.
M6 — CDC Setup
Enable ongoing replication Db2 → Azure SQL (DMS/CDC).
Run dual-sync for test workloads.
M7 — First Azure Service
Build Inventory microservice in AKS/App Service.
Consume replicated data (read-only).
M8 — Flip First Write Path
Orders created in Azure SQL.
Mirror writes back to Db2 for safety.
Validate via reconciliation reports.
M9 — Messaging Bridge
Set up Service Bus/Event Hubs.
Connect IBM MQ to Service Bus (Logic Apps or MQ on AKS).
Migrate non-critical queues.
M10 — Expand Azure Services
Add Pricing & Customer Update services.
Route both read/write to Azure SQL.
M11 — Consolidate Ownership
Promote Azure SQL as system of record for Orders & Products.
Legacy Db2 becomes consumer only.
M12 — Optimize & Decommission
Tune performance (autoscale, query tuning).
Reduce on-prem capacity or shut down slices.
Formal DR/BCP on Azure.
Exit criteria by Month 12:
✅ Order lifecycle runs entirely on Azure.
✅ At least 2 legacy domains retired.
✅ 99.9% uptime achieved.
✅ Cost tracking & governance live in Azure.
12-Month Replatform Migration Plan with Costs & Skills
M1 — Discovery & Strategy
Skills: Enterprise architect, business analyst, mainframe/RPG SME, Azure solution architect.
Costs: Mainly consulting/planning, ~5–10% of yearly budget.
M2 — Landing Zone & Connectivity
Skills: Azure networking/security engineer, infra architect.
Costs: ExpressRoute circuit, baseline Azure subscription, monitoring setup. Moderate CAPEX.
M3 — Data Assessment
Skills: Db2 DBA, Azure SQL DBA, migration specialist.
Costs: Tools (SSMA free, but staff time high). Low Azure consumption cost.
M4 — API Wrappers for Legacy
Skills: CICS/z/OS Connect SME, IBM i IWS/Node developer, API Mgmt engineer.
Costs: Middleware licensing, API Mgmt subscription.
M5 — Bulk Data Migration (Pilot)
Skills: Azure Data Factory engineer, DBA, QA testers.
Costs: ADF pipeline runs, Azure SQL MI capacity (small). Medium.
M6 — CDC Setup
Skills: CDC tool specialist, DBA, networking (low latency).
Costs: Azure DMS instance, extra bandwidth for replication. Ongoing cost.
M7 — First Azure Service
Skills: App Service/AKS developer, DevOps engineer.
Costs: AKS/App Service compute, CI/CD pipelines. Low/medium.
M8 — Flip First Write Path
Skills: Developers, QA, business testers, rollback/runbook writers.
Costs: Parallel run (double write = higher compute + DB cost).
M9 — Messaging Bridge
Skills: MQ admin, Azure Service Bus engineer, Logic Apps specialist.
Costs: Service Bus consumption, MQ bridge infra.
M10 — Expand Azure Services
Skills: Developers (Java/.NET), DevOps, security testers.
Costs: More App Services/AKS pods, higher Azure SQL load.
M11 — Consolidate Ownership
Skills: Data architect, DBA, application owner.
Costs: Azure SQL scales up, on-prem Db2 reduced (saves $$).
M12 — Optimize & Decommission
Skills: FinOps engineer, infra ops, cloud DBA.
Costs: Savings unlocked (legacy capacity down, Azure reservations in place).
Cost Curve (Approximate Trend)
Months 1–3 (Planning/Infra): Low-moderate.
Months 4–7 (APIs, Bulk, First services): Medium.
Months 8–10 (Dual-writes, bridges): High (double run).
Months 11–12 (Consolidation): Drops as legacy infra shrinks.
Team Composition (Core Roles Needed Throughout)
Azure Solution Architect (design overall flow).
Db2 DBA + Azure SQL DBA (dual until M11).
Mainframe/IBM i SMEs (integration + data mapping).
Developers (Java/.NET, RPG/COBOL wrappers) (services + APIs).
DevOps/SRE (CI/CD, observability, rollback).
FinOps (optimize spend, reservations).