How to Migrate from Oracle to PostgreSQL

Not only is PostgreSQL an open-source solution, but it also offers a host of benefits over Oracle—and that's why many companies are making the switch.

Here's what you need to know about the data migration process, the advantages of the transition, and the individual phases of adopting PostgreSQL that will guarantee success.

Why Move from Oracle to PostgreSQL?

Companies are seeing several advantages when they switch from Oracle to PostgreSQL, but some of the top benefits include the following;

• Reduced Cost: Aside from license costs, Oracle databases incur fees for partitioning, high availability, and other features, meaning costs quickly add up. PostgreSQL is an open-source solution, so it's free to install and free to use.
• Increased Flexibility: Aside from open-source licensing, PostgreSQL is easily used with the biggest cloud providers, including AWS. This helps prevent vendor lock-in.
• Greater Customizability: Countless extensions are available for PostgreSQL that can improve performance. Most are free to use, too, compared to Oracle's expensive add-ons.

Pre Check

Since migration from Oracle to PostgreSQL is time-consuming and a costly task as well, it's important to initially understand which part is for migration.

Avoid wasting time replicating data that you don't need in the future, such as backing up data from past maintenance.

The Oracle to PostgreSQL migration steps

Make sure you don't skip any of the 5 migration phases as explained below;

1. Assessment

A thorough assessment is the first step in planning a successful Oracle migration.

This requires you to analyze the difficulty of the migration and conduct research into technical issues while also evaluating compatibility between servers, features, data access, and so on.

The first phase should begin with an assessment of compatibility, as this is often regarded as such a basic concern that it ends up completely overlooked.

However, if you do not control your applications yourself, packaged software must be compatible with PostgreSQL.

If it isn't, you'll need to move to another application or ask the application's vendor to begin supporting PostgreSQL.

The next step is to evaluate your application code. If your applications rely on any Oracle-specific framework, the migration process will become much more time-consuming.

You'll need to factor in how many adjustments will need to take place to begin using PostgreSQL.

If you link to Oracle libraries or if you've embedded SQL, these adjustments can be of particular difficulty.

2. Schema Configuration

In Oracle, a schema is known as a user. By default, each Oracle user has their own schema, but in PostgreSQL, the schema name is not the same as the user name.

If you fail to specify a schema, new objects in PostgreSQL will default to a public schema.

An advantage to this is that users can create multiple schemas without needing to create new, separate users for each.

Still, you must migrate schemas correctly or you'll run into errors.

Fortunately, a number of migration tools exist that can automate the process—like Ora_migrator and Orafce.

3. Configuration Testing

Following schema configuration, the next phase in the migration process requires you to test the functionality of your PostgreSQL data.

Use a sample dataset to test your converted schema by loading sample data in PostgreSQL from a testing environment.

Ideally, you'll load the same test data into both PostgreSQL and Oracle.

Create an application connection and then perform some functional testing. The results should be the same for both PostgreSQL and Oracle.

If you run into any discrepancies between PostgreSQL and Oracle when using the test data, it's essential that you address them before bringing in additional data.

Test data should look identical in both databases, which means you have correctly configured your database before you clear out the test data and prepare for the actual migration.

4. Performance Testing

During the actual migration phase, it's important that you pause for a performance testing phase.

Oracle has many built-in functions and features that differ in PostgreSQL, and so your applications may not perform the same.

This phase allows you to understand those differences and address them one by one.

If you run into any performance issues, your team should take note of the problems and prioritize them accordingly.

Workarounds are possible, but they can take varying amounts of time depending on the discrepancy.

Stopping periodically for a performance test may be useful if you're working with many applications, especially if you're running into more than a few dependency issues.

5. Data Migration

When it comes time to actually migrate your data from Oracle to PostgreSQL, there are a few different approaches you can take.

Typically, these approaches are classified as the snapshot method, snapshot in parallel, or change data capture.

Snapshot means moving all data at once while snapshot in parallel means moving data in chunks, like with a schema or table.

Lastly, change data capture means data is loaded continuously using replication tools.

Each of these methods has pros and cons, and it's important that you select an approach based on the systems you're working with.

Make The Move to PostgreSQL

There are countless reasons to say goodbye to Oracle and make the move to PostgreSQL.

Whether you're being lured by the cost-savings, weary of potential vendor lock-in, or simply looking to enjoy the flexibility and customizability that PostgreSQL represents, the migration process doesn't have to take forever.

In fact, with the right experts by your side, making the move to PostgreSQL can be a relatively straightforward experience.

The key is to follow the established best practices and be sure that you don't skip the assessment and planning phases.

Adservio helps teams migrate from Oracle to PostgreSQL every day, and we can lend you a hand, too.

Interested in learning how to ease the transition and make the most of Postgres? Contact us today.