markus41 Migration Planner
Produce a complete data migration plan. This is the governing document for the migration engagement. It covers strategy selection, phase design, cutover planning, risk management, and go/no-go decision criteria. The output must be sufficient for a project sponsor to approve and a technical team to execute.
Migration Strategy Selection
Choose one of two strategies based on the factors below:
Big Bang Migration
All data migrated in a single cutover window. Old system decommissioned immediately.
Use when:
- Data volume is small enough to complete within the cutover window (typically < 4 hours of business downtime)
- Systems cannot run in parallel (licensing, data integrity, technical constraints)
- Business has tolerance for a planned maintenance window
- Data model is simple and migration is low-risk
Risks: If anything goes wrong during the window, rollback is the only option.
Phased Migration
Data migrated in multiple phases. Both systems run in parallel during the transition.
Use when:
- Data volume is too large for a single cutover window
- Business cannot accept extended downtime
- Migration has high complexity (multiple entity types with complex dependencies)
- Stakeholder confidence is best built by migrating lower-risk data first
Risks: Dual-system operation increases cost and complexity. Data must be kept synchronized during the parallel period.
Decision for this engagement:
| Factor | Assessment | Points Toward |
|---|---|---|
| Total data volume | [Volume] | Big Bang / Phased |
| Cutover window available | [Hours available] | |
| Business continuity requirement | [Can/cannot tolerate downtime] | |
| System parallel operation possible | Yes / No | |
| Migration complexity | Simple / Medium / Complex |
Selected strategy: [Big Bang / Phased] — [One paragraph rationale]
Phased Migration Design
(Complete this section only if phased migration is selected)
Phase definition principles:
- Migrate reference data first (agents, products, coverage types, lookup tables)
- Migrate master data second (clients, accounts)
- Migrate transactional data third (policies, loans, claims) in dependency order
- Migrate attachments and documents last (largest volume, least time-sensitive)
Phase plan:
| Phase | Name | Entities | Record Count | Est. Duration | Go-Live Date | Success Criteria |
|---|---|---|---|---|---|---|
| 0 | Reference Data | Agents, Products, Coverage Types, State Codes | ~500 records | 2 hours | [Date] | All reference records verified in destination |
| 1 | Master Data | Clients, Contacts | 12,450 | 4 hours | [Date] | 99.9% records migrated; reconciliation passed |
| 2 | Policies (Active) | Active policies only | 28,450 | 8 hours | [Date] | All active policies visible in new system; agents can work |
| 3 | Policies (Historical) | Cancelled, Expired policies | 9,750 | 4 hours | [Date] | Historical data available for lookup |
| 4 | Claims and Activities | Claims, Notes, Activities | 4,100 | 3 hours | [Date] | All open claims visible; closed claims accessible |
| 5 | Attachments | Document files | 28,000 files | 2 days | [Date] | All documents accessible via new system |
Verification gate between phases: After each phase completes, a defined reconciliation check must pass before the next phase begins. If the gate fails, pause and investigate before proceeding. Document the verification queries and acceptance criteria for each gate.
Dual-write period: During phases 2-4, new records created in the old system must also be captured and migrated to the new system. Specify:
- Delta capture mechanism: Change Data Capture (CDC) on source tables, or scheduled sync of modified_at timestamp
- Delta sync frequency: Every 4 hours during business hours
- Delta sync cutoff: T-24 hours before final cutover (last delta before final cutover)
- Final delta: Captured within the cutover window (old system in read-only mode)
Cutover Planning
Cutover Window Calculation
Estimate the cutover window duration:
| Task | Duration |
|---|---|
| Freeze source system (read-only mode) | 5 minutes |
| Final delta capture (records modified since last sync) | ~30 minutes (estimate) |
| Final delta load | ~15 minutes |
| Post-migration validation (automated reconciliation) | ~60 minutes |
| Business validation (key workflow smoke tests) | ~60 minutes |
| Go/no-go decision point | 15 minutes |
| User access switched to new system | 15 minutes |
| Rollback window (if go-live does not proceed) | ~120 minutes |
| Total cutover window | ~5-6 hours |
Cutover timing: Schedule the cutover window outside business hours. For insurance agencies: Friday evening or Saturday morning. For mortgage operations: avoid month-end (25th-5th of following month).
Cutover calendar:
- T-30 days: Complete final pre-migration dry run in test environment
- T-14 days: Confirm all data cleansing complete; final test migration
- T-7 days: Send user communication about cutover date and time
- T-3 days: Confirm rollback tested; confirm support team on standby
- T-1 day: Business owner sign-off on readiness; IT sign-off on environment
- T-0 (cutover day): Execute cutover runbook
Cutover Runbook
Numbered steps for the cutover execution team:
- Send "cutover starting" notification to all staff (email + Teams)
- Disable new record creation in source system (set to read-only or take offline)
- Record source record counts:
SELECT COUNT(*) FROM [each entity]— save to cutover log - Run final delta capture (modified_at > last sync timestamp)
- Load final delta to destination
- Run automated reconciliation: compare source counts to destination counts per entity
- Run business validation scenarios (see go/no-go criteria)
- Go/no-go decision meeting (15 minutes) — see criteria below
- If GO: Update DNS / URL configuration to point to new system; send go-live notification
- If NO-GO: Execute rollback procedure (see rollback-coordinator skill)
Dual-System Operation
During the parallel period (if phased), define which system is the system of record for each entity:
| Entity | System of Record | Read From | Notes |
|---|---|---|---|
| Agents | New system (after Phase 0) | New system | |
| Clients | Old system (until Phase 1 complete) | Old system | Sync to new system every 4 hours |
| Active Policies | Old system (until Phase 2 complete) | Old system | |
| New Policies written after Phase 2 | New system | New system | New business written in new system after Phase 2 |
Staff must know which system to use for which task during each phase. Provide a one-page reference card.
Risk Register
| # | Risk | Probability | Impact | Risk Score | Mitigation | Owner | Contingency |
|---|---|---|---|---|---|---|---|
| R-01 | Migration takes longer than cutover window | Medium | High | High | Dry run proves performance; have cloud scale-up ready | IT Lead | Execute rollback; reschedule cutover |
| R-02 | Data quality issues discovered during cutover | Low | High | Medium | Data profiling and dry run catch issues in advance | Data Lead | Rollback; fix data; reschedule |
| R-03 | Key business workflow fails in new system | Medium | High | High | UAT period includes all critical workflows | PM | Rollback; engage vendor support |
| R-04 | Delta capture misses records during parallel period | Low | High | Medium | Verify CDC configuration; monitor delta counts | IT Lead | Manual reconciliation; identify gaps |
| R-05 | Rollback fails (destination data corrupts source) | Very Low | Critical | High | Rollback tested in dry run; source system in read-only during cutover | IT Lead | Restore source from backup taken at T-0 |
| R-06 | Staff resistance to new system | Medium | Medium | Medium | Training completed before cutover; super-users identified | PM / Business | Extended parallel period; additional training |
| R-07 | Vendor support unavailable during cutover window | Low | High | Medium | Confirm vendor on-call support for cutover window | PM | Emergency escalation contact confirmed |
Go/No-Go Criteria Checklist
The go/no-go decision is made at Step 8 of the cutover runbook. All of the following must be met to proceed:
Automated validation (must pass 100%):
- Record count reconciliation: destination count = source count ± 0.01% for each entity
- Financial reconciliation: sum of PremiumAmount in destination = sum in source ± $0.01
- Zero critical errors in migration job log
- Referential integrity check: zero orphaned records in destination
- RLS / permissions check: test user can access only their authorized data
Performance validation:
- New system page load time < 3 seconds for key screens
- Report query completes in < 30 seconds for standard reports with full data volume
Business validation (business owner confirms):
- Look up 5 specific client records by name — all found with correct data
- Look up 5 specific policy records by policy number — all found with correct premium
- Run standard production report — data matches source system report
- Create a new test record — saves successfully
- Retrieve a document attachment — opens correctly
Organizational readiness:
- All staff training completed (training completion rate > 95%)
- Super-users briefed and available for cutover day
- IT support team on standby for 48 hours post-cutover
- Vendor support confirmed on call
Rollback readiness:
- Source system backup confirmed and restorable (tested T-3 days)
- Rollback procedure rehearsed and documented
- Rollback decision authority confirmed (who can call rollback and when)
Rollback point of no return: Rollback is feasible until T+4 hours after user access is switched to the new system. After T+4 hours, new records created in the destination make rollback impractical. The go/no-go meeting must surface any critical issues before this window closes.
Output Format
Deliver as:
- Migration strategy decision with rationale
- Phase plan table (if phased) with entity list, record counts, durations, and success criteria
- Delta sync specification (mechanism, frequency, cutoff)
- Cutover window calculation table
- Cutover runbook (numbered steps)
- Dual-system operation reference (which system for which task, per phase)
- Risk register (full table with all fields)
- Go/no-go criteria checklist (formatted as a checklist with sign-off lines)
- Project timeline (phases → testing → training → dry run → cutover)
- Communication plan (who is notified, when, with what message, for each major milestone)