Minute-by-Minute Migration War Room Script (Banking System: Oracle → MongoDB on Azure VM)
This is a real-world, production-grade war room script designed for a mission-critical banking migration with:
10TB–100TB data
Near-zero downtime
Full auditability
Senior DBA will act as the Migration Commander.
WAR ROOM TEAM STRUCTURE (Assign Before Start)
Each role must be assigned clearly:
Migration Commander (Senior DBA) → decision maker
Oracle DBA → source system control
MongoDB Engineer → target system
Application Owner → app switch
Network Engineer → connectivity
Audit/Compliance Officer → logging & approvals
Scribe (very important) → records every action
T-60 MINUTES (1 Hour Before Cutover)
Objective: Final readiness check
Commander Says:
“Team, we are entering T-60. Confirm readiness.”
Checklist
✔ All migration scripts tested
✔ MongoDB cluster healthy
rs.status()
✔ Disk space verified
df -h
✔ Backup completed (FINAL Oracle backup)
expdp system/password FULL=Y DUMPFILE=final_backup.dmp
✔ Rollback plan confirmed
Decision Gate:
If ANY issue → DELAY migration
T-45 MINUTES
Objective: Freeze non-essential systems
Commander Says:
“Freeze all non-critical jobs.”
✔ Stop batch jobs
✔ Disable scheduled jobs
BEGIN
DBMS_SCHEDULER.DISABLE('JOB_NAME');
END;
✔ Notify business users
T-30 MINUTES
Objective: Prepare for final sync
✔ Verify last incremental sync timestamp
✔ Run pre-cutover incremental extraction:
SELECT * FROM transactions
WHERE last_updated > :last_sync_time;
✔ Prepare MongoDB import scripts
Commander Checkpoint
“Is incremental pipeline ready?”
T-15 MINUTES
Objective: Enter controlled shutdown mode
Commander Says:
“Prepare to stop writes.”
✔ Application switched to READ-ONLY mode
✔ Confirm:
No new transactions
No writes happening
T-10 MINUTES
Objective: Stop Oracle writes completely
✔ Stop application services
✔ Confirm zero active sessions:
SELECT COUNT(*) FROM v$session WHERE status='ACTIVE';
Must be 0 or near zero
T-5 MINUTES (CRITICAL POINT)
Objective: Final incremental sync
Commander Says:
“Execute FINAL SYNC now.”
✔ Extract final delta:
SELECT * FROM transactions
WHERE last_updated > :cutover_time;
✔ Convert to JSON
✔ Load into MongoDB:
mongoimport --file final_delta.json --collection transactions
T-0 (CUTOVER MOMENT)
Objective: Switch system to MongoDB
Commander Says (Very Clearly):
“Cutover initiated. Switch application to MongoDB.”
✔ Update application connection string
✔ Start application services
✔ Smoke test:
Login works
Transactions work
Queries return results
T+5 MINUTES
Objective: Immediate validation
✔ Check MongoDB health:
db.serverStatus()
✔ Check replication:
rs.status()
✔ Run transaction test:
db.transactions.findOne()
T+10 MINUTES
Objective: Financial validation (MOST IMPORTANT)
Commander Says:
“Run financial reconciliation.”
✔ Oracle total:
SELECT SUM(amount) FROM transactions;
✔ MongoDB total:
db.transactions.aggregate([
{ $group: { _id: null, total: { $sum: "$amount" } } }
])
Decision:
Match → continue
Mismatch → ROLLBACK immediately
T+15 MINUTES
Objective: Monitor system stability
✔ Check logs:
tail -f /var/log/mongodb/mongod.log
✔ Check errors
✔ Check latency
T+30 MINUTES
Objective: Business validation
✔ Business users test:
Account balance
Transaction history
Payments
Commander Question:
“Business, do you confirm system correctness?”
T+45 MINUTES
Objective: Performance monitoring
✔ Check slow queries
db.setProfilingLevel(1)
✔ Check CPU / Memory
T+60 MINUTES (STABILIZATION COMPLETE)
Objective: Declare success
Commander Says:
“Migration successful. Entering monitoring phase.”
✔ Keep Oracle in read-only fallback mode
✔ Do NOT decommission yet
ROLLBACK PLAN (IF SOMETHING FAILS)
Trigger Conditions:
Financial mismatch
Missing transactions
Application failure
Rollback Steps
Commander Says:
“Rollback initiated. Reverting to Oracle.”
✔ Stop application
✔ Reconnect to Oracle
✔ Restart services
✔ Validate Oracle system
Target rollback time:< 15 minutes
Example Dialogue
Commander:
“Team, confirm MongoDB primary is healthy.”
Mongo Engineer:
“Primary is stable, replication lag 0 seconds.”
Commander:
“Oracle DBA, confirm no active transactions.”
Oracle DBA:
“Confirmed, zero active sessions.”
Commander:
“Proceed with final sync.”
Scribe logs everything.
COMMON FAILURE SCENARIOS
Issue 1: Missing Transactions
Fix:
Re-run incremental sync
Compare IDs
Issue 2: Slow MongoDB Queries
Fix:
Add index immediately
db.transactions.createIndex({ account_id: 1 })
Issue 3: Replication Lag
Fix:
Check network
Reduce write load
POST-WAR ROOM (FIRST 24 HOURS)
✔ Monitor every 15 minutes
✔ Keep full team on standby
✔ Do NOT relax monitoring
FINAL ADVICE (FROM REAL MIGRATIONS)
The cutover is only 5% of the work
The validation is 95%
Always trust numbers, not assumptions
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