Oracle Zero Downtime Migration (ZDM) - Introduction

Oracle Zero Downtime Migration (ZDM) Explained in Detail

What is ZDM?

Oracle Zero Downtime Migration (ZDM) allows you to directly migrate

your Oracle Database to the Oracle Cloud from various Oracle

Database versions into different target cloud deployments depending

on your requirements and business needs.

How does it work?

What Happens in ZDM?

● ZDM software is installed on ZDM host which connects to source

and target to perform the migration process.

● ZDM is tooling on top of Oracle Data Guard, Data Pump and

Goldengate technologies.

● ZDM tooling allows customers to invoke and perform the

migration without knowing the details of the underlying process.

● ZDM has MySQL database to keep track of progress.

ZDM - Before Migration

● ZDM host should be running Oracle Linux 7 or later and latest version of ZDM is 21.4.

● ZDM host can be on-premise or cloud.

● Source database should be Oracle Database 11GR2 (11.2.0.4) or later.

● Source database must be in archive log mode.

● TDE Wallet should be open on PDB and CDB on source DB.

● Target database must be same version as the source database for physical migration.

● Target database to be created before the migration and ready.

● Target database db_name should match with source database.

● Source and target database should have access to object storage.

ZDM - Physical Online Migration

● Backs up the source database to the specified data transfer medium.

● Instantiates a standby database from this backup to the target environment.

● Configures Data Guard with Maximum Performance protection mode and asynchronous

(ASYNC) redo transport mode.

● Synchronizes the source and target databases.

● Switches over to the target database as the new primary database with minimum downtime.

ZDM - Physical Offline Migration (RMAN)

● Zero Downtime Migration can perform a backup and restore operation to achieve an offline

physical migration using RMAN.

● Backs up the source database to the specified data transfer medium.

● Instantiates a new database from this backup to the target environment.

● The offline migration method is similar to cloning a database. The target database has no

relationship to the source, so there is no data synchronization or fallback capability. No

SQL*Net connectivity is needed between the source and target database servers.

*While Standard Edition databases can use Zero Downtime Migration, they must use the

offline migration method which is based on a backup and restore methodology that does

not use Data Guard.

ZDM - Logical Online Migration (GoldenGate)

● Zero Downtime Migration harnesses Oracle GoldenGate and Oracle Data Pump to perform an

online logical migration.

During a logical online migration, the source database remains online for client connections while

data is moved to the target database, using a combination of Oracle Data Pump and Oracle

GoldenGate replication.

Logical online migration involves two steps:

● Instantiation of target database.

● Oracle Data Pump extracts data from the source database and loads it into the target

database.

● Real-time data replication between source and target databases.

ZDM - Logical Offline Migration (DataPump)

● Zero Downtime Migration can perform an offline logical migration using Oracle Data Pump to extract

the data from the source database and load it into a target database.

● Offline logical migration means that the source database is not available for clients while data is

moved to the target database. When using the offline migration method,

● You must stop updates to the source database before you start a migration. When the migration is

complete, the target database and source database do not require any direct SQL*Net connectivity

between them.