Lesson 5: Comparing ZDM vs GoldenGate vs RMAN

Ashish Agnihotri

Data Analyst at Exaguru 

Introduction

When planning database migrations to OCI, ExaCC, or ExaCS, Oracle provides multiple tools and approaches:
  • Zero Downtime Migration (ZDM) → Automation & orchestration layer.
  • Oracle GoldenGate (OGG) → Logical replication engine.
  • Recovery Manager (RMAN) → Backup & restore framework.
Choosing the right method depends on database version, platform, downtime tolerance, and complexity. This lesson compares these three approaches.

🔹 Technical Architecture Overview

1. ZDM (Zero Downtime Migration)

  • Role: Orchestrates end-to-end migration.
  • Tech Stack: Uses RMAN, Data Guard, or GoldenGate under the hood.
  • Automation: Handles pre-checks, monitoring, logging, and cutover.
  • Target: OCI DB Systems, Exadata, ExaCC.
  • Downtime: Minimal (minutes).

2. Oracle GoldenGate

  • Role: Logical replication at the transaction level.
  • Tech Stack: Extract/replicate processes for continuous sync.
  • Use Case: Heterogeneous migrations (different platforms, endian conversion).
  • Target: On-prem, OCI, multi-cloud.
  • Downtime: Near zero (cutover only).

3. RMAN (Recovery Manager)

  • Role: Backup/restore for physical migration.
  • Tech Stack: RMAN backups applied to the target.
  • Use Case: Homogeneous migrations (same endian, platform).
  • Target: On-prem, OCI DB Systems, Exadata.
  • Downtime: Medium to high (hours).

🔹 Comparitive Table

Feature / Tool   ZDM GoldenGate RMAN
Automation   ✅ Full orchestration (pre-check → cutover)     ❌ Manual setup     ❌ Manual setup  
Downtime   ⏳ Minutes (minimal)   ⏳ Near zero      ⏳ Hours (depends on DB size)  
Cross-Version   ✅ Yes (11g → 19c/21c)     ✅ Yes     ⚠️ Limited (requires upgrade after restore)
Cross-Platform   ✅ Yes (via OGG/RMAN)     ✅ Yes     ❌ No (same platform only)  
Complexity   🔽 Low (CLI-driven)     🔼 High (multiple configs)     🔼 High (scripts, staging)  
Monitoring   ✅ Centralized ZDM logs     ⚠️ Separate OGG logs     ⚠️ Separate RMAN logs  
Best For   Enterprise migrations to OCI/ExaCC     Heterogeneous, 24x7 workloads     Simple, same-platform upgrades  


🔹 Workflows

ZDM Workflow (Data Guard mode)

 Pre-check → Standby Creation → Continuous Sync → Cutover → Post-validation

GoldenGate Workflow

 Extract → Trail Files → Replicat → Sync → Cutover

RMAN Workflow

 Backup → Transfer → Restore → Upgrade → Validate

🔹 Example Commands

  
ZDM Pre-check
 zdmcli migrate database \

                
    -sourcedb myDB \

                
    -targetdb myTargetDB \

                
    -mode dg \

                
    -precheck 

                
GoldenGate Extract Setup

                
 ADD EXTRACT ext1, TRANLOG, BEGIN NOW

                
 ADD EXTTRAIL ./dirdat/lt, EXTRACT ext1 

                
RMAN Backup & Restore

                
 rman target / RMAN>

                
 BACKUP DATABASE PLUS ARCHIVELOG;

                
 RMAN> RESTORE DATABASE;

🔹 Best Practices

  • Use ZDM for large-scale, automated migrations to OCI/ExaCC.
  • Use GoldenGate when downtime must be almost zero or when migrating across heterogeneous platforms.
  • Use RMAN for small to mid-size databases on the same platform where downtime is acceptable.
  • For 11g → 19c upgrades, ZDM + RMAN/GoldenGate combo is the safest path.

🔹 Closing Thoughts

  • ZDM is the strategic orchestration framework for modern Oracle migrations.
  • GoldenGate remains the gold standard for heterogeneous, near zero-downtime migrations.
  • RMAN is still useful for simple, same-platform migrations.
Together, they form a migration toolkit that DBAs and architects can combine based on business needs, SLAs, and complexity.
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