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  • User AvatarPradip
  • 11 Dec, 2025
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  • 4 Mins Read

PDB Migration Techniques for Multitenant Architecture

Introduction

Oracle Multitenant Architecture allows organizations to run multiple pluggable databases (PDBs) within a single container database (CDB). As databases grow and environments change, migrating PDBs becomes essential—whether for resource optimization, version upgrades, moving to cloud, or consolidation.

This blog explains all major PDB migration techniques, when to use them, step-by-step workflows, benefits, limitations, and real-world use cases.

PDB Migration Techniques for Oracle Multitenant Architecture

Why is PDB Migration Needed?

PDB migration is common in:

1. Data Center Migration

Moving PDBs between on-prem servers or cloud.

2. Hardware Upgrade

Shifting PDBs to new servers with better CPU, RAM, or storage.

3. CDB Patch/Upgrade Consolidation

Migrating PDBs to a new version of the CDB.

4. Workload Balancing

Distributing PDBs across multiple CDBs to avoid performance bottlenecks.

H3: 5. Development to Production Move

Cloning or migrating PDBs to other environments.

Key PDB Migration Techniques

Below are the most common and recommended techniques for Oracle DBAs:

1. Unplug/Plug Method

Overview

This is the most traditional migration method, used when moving a PDB between CDBs with the same version.

Steps

  1. Close the PDB:

    ALTER PLUGGABLE DATABASE pdb1 CLOSE IMMEDIATE;

  2. Unplug the PDB:

    ALTER PLUGGABLE DATABASE pdb1 UNPLUG INTO '/backup/pdb1.xml';

  3. Copy datafiles to target CDB.

  4. Plug into new CDB:

    CREATE PLUGGABLE DATABASE pdb1 USING '/backup/pdb1.xml' COPY FILE_NAME_CONVERT=('old','new');

  5. Run PDB compatibility check and fix violations.

  6. Open PDB:

    ALTER PLUGGABLE DATABASE pdb1 OPEN;

Advantages

  • Clean migration

  • Easy validation

  • Supports metadata transport

Limitations

  • Requires downtime

  • CDB versions must match

2. PDB Cloning (Local Cloning)

Overview

Used to create a copy of a PDB on the same CDB.

Steps

CREATE PLUGGABLE DATABASE pdb_clone FROM pdb1;
ALTER PLUGGABLE DATABASE pdb_clone OPEN;

Use Cases

  • Quick dev/test environment creation

  • Data masking

  • Zero-impact testing

3. Remote Cloning (Cross-CDB Migration)

Overview

Cloning a PDB from a remote CDB using a database link.

Steps

  1. Create DB link to source CDB.

  2. Execute:

    CREATE PLUGGABLE DATABASE pdb_remote_clone FROM pdb1@source_link;

  3. Open with required conversions.

Benefits

  • Requires minimal downtime

  • No need to manually transfer files

  • Ideal for on-prem to cloud migration

4. Refreshable PDB (Incremental Migration)

Overview

A refreshable PDB maintains incremental sync with a source PDB.

Key Commands

CREATE PLUGGABLE DATABASE pdb_ref FROM pdb1@source_link REFRESH MODE MANUAL;
ALTER PLUGGABLE DATABASE pdb_ref REFRESH;

Benefits

  • Near-zero downtime during cutover

  • Best for production migrations

  • Works for cloud onboarding (OCI)

5. Transportable Tablespaces for PDB Migration

Overview

Used when only specific schemas/tablespaces need to be migrated.

Steps

  • Set tablespaces READ ONLY

  • Export metadata

  • Transfer datafiles

  • Import into target CDB

Use Cases

  • Partial migrations

  • Schema-level transport

  • Moving large datafiles efficiently

6. Data Pump Export/Import (Full/Schema-Level)

Overview

A universal migration approach, works across different Oracle versions.

Steps

  1. Export PDB/Schemas:

    expdp system/password FULL=Y DIRECTORY=dpdir DUMPFILE=pdb.dmp

  2. Copy dump file to target server.

  3. Import into target CDB/PDB:

    impdp system/password FULL=Y DIRECTORY=dpdir DUMPFILE=pdb.dmp

When to Use

  • Version upgrade

  • Cross-platform migration

  • When other PDB methods fail

Limitations

  • Slow for large datasets

  • Needs downtime

7. GoldenGate for Real-Time PDB Migration

Overview

Oracle GoldenGate enables zero-downtime PDB migration through real-time replication.

Process

  • Configure extract on source PDB

  • Configure replicat on target PDB

  • Sync data in near real-time

  • Perform cutover

Best For

  • Cloud migrations

  • Active-active setups

  • High Availability

Choosing the Right PDB Migration Technique

Based on Downtime

  • Zero downtime: GoldenGate, Refreshable PDB

  • Low downtime: Remote Cloning

  • High downtime acceptable: Unplug/Plug

Based on Environment

  • Same version CDB: Unplug/Plug

  • Cross-version upgrade: Data Pump

  • Large DB: Transportable Tablespaces

Best Practices for Smooth PDB Migration

1. Validate PDB Compatibility

Use:

SET SERVEROUTPUT ON
DECLARE
errors number;
BEGIN
errors := DBMS_PDB.CHECK_PLUG_COMPATIBILITY(...);
END;
/

2. Check Character Set Compatibility

3. Check Undo Mode (Local vs Shared)

4. Ensure Proper Backup Before Migration

5. Clean Up Invalid Objects After Migration

FAQs: PDB Migration Techniques

Q1. Can I migrate a PDB to a CDB with a different Oracle version?

Yes, but not using unplug/plug. Use Data Pump or GoldenGate.

Q2. Which migration technique offers zero downtime?

Oracle GoldenGate and Refreshable PDB provide near-zero downtime.

Q3. Is CDB-compatible version mandatory for unplug/plug?

Yes. Both CDBs should be on the same version and patch level.

Q4. What is the fastest PDB migration method?

Remote cloning and transportable tablespaces are fastest for large databases.

Q5. How do I migrate only selected schemas?

Use transportable tablespaces or Data Pump schema-level export/import.

Conclusion

Oracle Multitenant Architecture provides multiple flexible and efficient PDB migration techniques. The right method depends on your project requirements—downtime tolerance, data size, CDB version, and environment. Whether you choose unplug/plug, remote cloning, refreshable PDBs, transportable tablespaces, or GoldenGate, proper planning ensures a smooth migration with minimal risks.

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