Info2soft use cookies to help you have a superior and more admissible browsing experience on our website. Privacy Policy
Loading...
By:
Migrating an Oracle database to PostgreSQL is more than transferring tables and records. Differences in data types, SQL syntax, database objects, application dependencies, and ongoing data changes can all affect the migration process.
A successful Oracle to PostgreSQL migration therefore requires a structured approach that covers the entire process—from assessing the source database and preparing the PostgreSQL environment to synchronizing ongoing changes and switching production applications to the new platform.
Organizations may move from Oracle to PostgreSQL as part of database modernization, infrastructure changes, or efforts to reduce dependence on proprietary database platforms.
PostgreSQL provides an open-source relational database platform that can be used across on-premises, cloud, and hybrid environments. For organizations planning to modernize their database infrastructure, PostgreSQL can be a suitable target platform.
However, the migration process requires careful planning. Oracle and PostgreSQL differ in data types, SQL syntax, procedural languages, and database features. These differences need to be addressed before production applications are moved.
The goal is therefore not simply to move data, but to create a PostgreSQL environment that can reliably support the applications and workloads previously running on Oracle.
Before starting an Oracle PostgreSQL migration, identify the differences that may affect the target environment.
Oracle and PostgreSQL use different data types and may handle similar data differently.
Common mappings include:
| Oracle | PostgreSQL |
|---|---|
| VARCHAR2 | VARCHAR / TEXT |
| NUMBER | NUMERIC / INTEGER / BIGINT |
| CLOB | TEXT |
| BLOB | BYTEA |
| DATE | DATE / TIMESTAMP |
These mappings should be reviewed based on the actual data and application requirements rather than treated as automatic one-to-one conversions.
For example, an Oracle NUMBER column may need to become INTEGER, BIGINT, or NUMERIC in PostgreSQL depending on the values it stores and the required precision.
Applications and database objects may rely on Oracle-specific SQL or PL/SQL features.
Stored procedures, functions, triggers, packages, hierarchical queries, sequences, and other Oracle-specific logic may require conversion or rewriting for PostgreSQL.
SQL compatibility should therefore be assessed before the migration rather than discovered during the final cutover.
A database migration involves more than moving table data.
Depending on the environment, the migration may also need to address:
Tables and columns
Primary and foreign keys
Indexes
Sequences
Views
Functions and procedures
Triggers
Constraints
Dependencies between these objects should be reviewed so that the PostgreSQL environment can be prepared in the correct order.
Applications may also depend on Oracle-specific behavior.
Before moving production workloads, review:
SQL queries
Database drivers
Connection settings
Stored procedure calls
Oracle-specific application logic
Transaction behavior
Application testing against PostgreSQL is an important part of the migration process because a database that contains the correct data may still require application-side changes before it can replace Oracle.
For a small database, it may be possible to stop the application, migrate the data, validate the target database, and then restart the application.
Production databases are often different.
If Oracle continues receiving inserts, updates, and deletes while the migration is underway, the target PostgreSQL database can become outdated after the initial data load.
This creates a key distinction:
Initial Data Migration moves the existing database.
Continuous Synchronization keeps the target database updated with changes made after the initial migration.
For production environments, both may be required.
A structured migration can be divided into five main stages.
Start by documenting the source environment before moving production data.
Review:
Database size and growth
Tables and schemas
Data types
Indexes and constraints
Views and triggers
Sequences
Stored procedures and functions
Application dependencies
Acceptable downtime
This assessment helps determine the scope of schema conversion and whether an offline or phased migration approach is more appropriate.
It is also useful to identify critical tables and applications early so that they can receive additional validation during the migration.
Prepare the PostgreSQL target environment before transferring production data.
Create or convert the required:
Schemas
Tables
Columns
Data types
Constraints
Indexes
Sequences
Views
Functions
Triggers
Oracle-specific SQL and PL/SQL logic may need to be converted to PostgreSQL-compatible alternatives.
Testing the converted schema before the main data migration can help identify compatibility issues early and reduce problems during cutover.
Once the target schema is ready, migrate the existing Oracle data to PostgreSQL.
Depending on the environment, organizations may use:
CSV or other intermediate files
Database migration utilities
ETL processes
Bulk data loading
Replication-based migration tools
For smaller databases, a batch migration may be sufficient.
For larger production databases, the initial load is often only the first stage of the migration. Changes made in Oracle after the initial load still need to be synchronized before the final cutover.
This step becomes important when the Oracle database must remain operational during migration.
Consider a database where the initial data load takes several hours. During that period, users may continue creating, updating, or deleting records in Oracle.
The PostgreSQL database would then contain the data that existed at the beginning of the migration, but not necessarily the latest changes.
Continuous synchronization addresses this gap by replicating subsequent changes from Oracle to PostgreSQL.
The migration process can therefore follow this model:
Oracle Database → Initial Data Load → PostgreSQL
while ongoing changes are synchronized through:
Oracle Database → Continuous Replication → PostgreSQL
This allows the target environment to be prepared and tested before production traffic is switched.
Before moving applications to PostgreSQL, validate the target environment.
Important checks include:
Row counts
Data consistency
Primary and foreign key relationships
Indexes and constraints
Critical queries
Stored procedures and functions
Application connectivity
Performance
Replication status
Once the PostgreSQL environment has been validated, perform the final synchronization and switch the application to the new database.
A rollback plan should also be prepared before the production cutover.
There is no single migration method that fits every Oracle environment. The appropriate approach depends on database size, application requirements, data transformation needs, and acceptable downtime.
| Migration Method | Suitable For | Continuous Synchronization |
|---|---|---|
| Batch Migration | Small or controlled migrations | No |
| FDW | Specific data access and integration scenarios | Limited |
| ETL / Migration Tools | Bulk migration and data transformation | Depends on the tool |
| Real-Time Replication | Production migrations requiring ongoing synchronization | Yes |
Batch migration transfers data during a defined migration window.
It can be suitable when the database is relatively small or planned downtime is acceptable.
Its main limitation is that changes made in Oracle after the initial export are not automatically included unless an additional synchronization process is used.
PostgreSQL Foreign Data Wrappers can provide access to external data sources and may be useful for specific integration or migration scenarios.
However, FDW-based access should not automatically be treated as a complete production migration strategy, particularly when continuous synchronization and application cutover are required.
Migration and ETL tools can help automate schema conversion, data transformation, and bulk data movement.
They can be useful for complex migration projects, but the resulting PostgreSQL environment still needs compatibility testing and data validation.
For production environments where Oracle must remain available during migration, real-time replication provides another approach.
The initial database can be loaded into PostgreSQL first, while subsequent changes are continuously replicated from Oracle.
This allows the target environment to be prepared and validated before the final cutover.
For production databases, the objective is often not to eliminate every second of downtime, but to reduce the amount of work that must be completed during the final cutover.
A phased approach can separate the migration into four stages:
Transfer the existing Oracle data to PostgreSQL.
Keep PostgreSQL updated with changes made in Oracle while the source database remains operational.
Test data consistency, database objects, queries, and applications against PostgreSQL.
Complete the remaining synchronization and switch applications to PostgreSQL.
This approach separates most of the migration workload from the final cutover window and can help reduce business disruption.
For production migrations that require continuous synchronization, i2Stream supports heterogeneous, real-time database replication between Oracle and PostgreSQL.
Instead of relying only on a one-time data transfer, i2Stream can capture and replicate ongoing database changes while the PostgreSQL environment is being prepared and validated.
Heterogeneous Database Replication — Synchronize data between different database platforms.
Real-Time Data Synchronization — Replicate ongoing database changes during migration.
DML and DDL Replication — Support changes to data and database structures.
Data Comparison — Compare source and target data to help validate migration results.
A migration using this approach can follow:
Initial Data Load → Continuous Synchronization → Validation → Final Cutover
This allows organizations to prepare the PostgreSQL environment while Oracle remains in operation and helps reduce the amount of migration work required during the final cutover.
Assess database size and dependencies
Review Oracle-specific database objects
Identify data type differences
Review SQL and PL/SQL compatibility
Check application dependencies
Define downtime requirements
Select the migration approach
Convert the PostgreSQL schema
Perform the initial data load
Synchronize ongoing changes when required
Monitor migration or replication status
Validate critical data
Test applications against PostgreSQL
Verify data consistency
Check critical queries and database objects
Confirm synchronization status
Complete the final synchronization
Prepare a rollback plan
Switch applications to PostgreSQL
Can I migrate Oracle directly to PostgreSQL?
Yes. Oracle databases can be migrated to PostgreSQL, but the process usually requires schema conversion, data type mapping, SQL or PL/SQL adjustments, data transfer, and validation.
What tools can be used to migrate Oracle to PostgreSQL?
Oracle to PostgreSQL migrations can use batch export and import methods, ETL and migration utilities, or real-time database replication tools. The appropriate approach depends on database size, schema complexity, transformation requirements, and downtime requirements.
What are the main challenges when migrating Oracle to PostgreSQL?
Common challenges include data type differences, SQL and PL/SQL compatibility, database object conversion, application dependencies, data consistency, and maintaining the source database while migration is in progress.
How can I migrate Oracle to PostgreSQL with minimal downtime?
A common approach is to perform the initial data migration first, continuously synchronize changes from Oracle to PostgreSQL, validate the target environment, and then perform a final cutover.
Can Oracle and PostgreSQL run in parallel during migration?
Yes. Running Oracle and PostgreSQL in parallel can be part of a phased migration strategy. Continuous synchronization can help keep PostgreSQL updated while applications continue using Oracle until the final cutover.
· Enterprise & Mid-market Customers Worldwide
· Support team available to assist you throughout your trial
· Start a 60-day free trial or view demo to see how Info2Soft protects enterprise data.
