Oracle Zero Downtime Migration(Oracle ZDM) - Overview

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Oracle ZDM is a software solution which allows you to directly and seamlessly migrate your on-premises Oracle Databases to and between any Oracle-owned infrastructure, including Exadata Database Machine On-Premises, Exadata Cloud at Customer (ExaC@C), and Oracle Cloud Infrastructure.

Oracle Zero Downtime Migration (ZDM) is designed using Oracle's best practices for high availability. It uses tools like Golden-Gate and Data Guard to keep your database available during migration, and relies on technologies such as RMAN, Data Pump, and database links to move data efficiently and safely — all with minimal downtime.

Oracle ZDM offers four different migration methods:

1. Logical Online Migration using Golden-Gate.

    In  logical online migration approach ZDM leverages Oracle Data Pump for the initial export and Oracle Golden-Gate for continuous data replication. Oracle Golden-Gate plays a critical role by capturing and applying real-time changes from the source to the target database, ensuring both remain in sync throughout the migration. This allows applications to keep running without interruption. Once the target is fully synchronized, ZDM performs a brief cutover to switch operations. Oracle Golden-Gate real-time replication capability makes this approach ideal for migrating active, business-critical databases seamlessly.









2. Logical Offline Migration using Data Pump.

In logical offline migration approach Oracle ZDM uses Oracle Data Pump to export data from the source database and import it into the target. During this process, the source database remains offline, resulting in downtime. It migrates schema objects, data, and metadata without requiring Oracle Golden-Gate. This approach is simpler and does not need a separate replication setup. It is ideal for non-critical systems where some downtime is acceptable.












3. Physical Online Migration using Data Guard.

In physical online migration Oracle ZDM uses Oracle Data Guard to enable minimal downtime migration by creating a physical standby of the source database on the target system. Oracle ZDM server host connects to both source and target database host and uses RMAN to duplicate the database and keeps the standby continuously synced with the source using Data Guard's redo apply. The source database remains online throughout the process. During cutover, ZDM performs a switchover to make the standby the new primary. This method ensures a reliable, low-downtime migration and does not require a Golden-Gate license.













4. Physical Offline Migration using RMAN.

Oracle ZDM's physical offline migration uses RMAN to back up the source database and restore it on the target system. The source database is shutdown/mounted during the process, resulting in complete downtime. This approach creates an exact physical copy, including data files, control files, and archive logs. It is simpler and does not require Oracle Golden-Gate or Data Guard. Physical offline migration is suitable for environments where downtime is acceptable.












Oracle ZDM allows the source database to be a non-CDB or a container database (CDB) with one or more Pluggable Databases (PDBs). 

Starting with release 21.1, Oracle ZDM allows non-CDB Databases to be migrated to Pluggable Databases on the fly, allowing for total conversion and adding more versatility to the migration workflow.

Supported Sources:

Database Versions Supported Configuration
Oracle Database 11g Oracle Database single instances
Oracle Database 12c Oracle Real Application Clusters (RAC) one-node databases
Oracle Database 18c Oracle Real Application Clusters (RAC) databases
Oracle Database 19c and later

Supported Targets Oracle Database Cloud Services :

Supported Targets - Oracle Database Cloud Services
Oracle Base Database Service
Oracle Enterprise Database Service
Oracle Exadata Database Service on Dedicated Infrastructure
Oracle Exadata Database Service on Cloud@Customer
Oracle Autonomous Database - ATP
Oracle Autonomous Database - ADW
Exadata Database Machine On-Premises

The Zero Downtime Migration software offers a command line interface that you install and run on a host that you provision. The server where the Zero Downtime Migration software is installed is called the Zero Downtime Migration service host. You can run one or more database migration jobs from the Zero Downtime Migration service host. 

In our next blog post, we'll dive into the installation and configuration of Oracle Zero Downtime Migration (ZDM), providing a step-by-step guide to help you get started seamlessly.



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