What is Database Migration?
Database migration is moving data to new systems for better performance, lower costs, or modernization. This guide explores the entire process, including different types, strategies, key benefits, common risks, and best practices for a successful transfer.
Understanding Database Migration
Database migration is the process of moving data from one database system (the source) to a different one (the target). This transfer can involve moving data between:
- Different physical locations, such as from an on-premise data centre to a cloud platform.
- Different database technologies, like migrating from an Oracle database to a MySQL database, or from a relational database to a non-relational one.
- Different versions of the same database software are in use, such as upgrading to the latest version.
At its core, database migration of every database table and column is driven by the need to evolve for users. Common reasons for a migration include modernizing legacy applications, reducing costs, improving performance and scalability, consolidating databases after a merger, or enabling new analytics capabilities.
While it may sound like a simple "copy and paste" operation, a database migration is a complex process. It requires careful planning to ensure that data is transferred completely, accurately, and securely, often while minimizing downtime for the applications that depend on it.
How Does Database Migration Work?
A cloud migration where a database is involved isn't a single event but a carefully orchestrated project. To ensure data is moved securely, accurately, and with minimal disruption, the process is typically broken down into three main phases: thorough planning, active execution, and final validation.
Pre-Migration planning and preparation
This initial phase is the most critical for success. It involves a thorough assessment of the source database and each table and column to understand the data, schema, and dependencies used in the database management system.
Teams define clear business goals, choose a migration strategy (such as "lift-and-shift" or a phased approach), and select the right tools. A key part of this stage is designing the target database's schema and, most importantly, performing a full backup of the source database to ensure a safe rollback path in case of any use failures.
Data Extraction, transformation, and loading (ETL)
ETL is the execution phase when we migrate, where data is actively moved. First, data is extracted from the source database.
Then, it undergoes transformation, which is especially crucial in heterogeneous migrations (moving between different database types); this step cleans, reformats, and creates a remap of the data to fit the structure and rules of the new target database. Finally, the transformed data is loaded into the target database.
Post data migration validation and cutover
After the data is loaded, it must be rigorously validated to ensure no data was lost or corrupted during the transfer. This involves running tests, comparing row counts, and sampling data. At the same time, applications are tested against the new database.
Once all tests are passed, the team performs the final cutover, where the live application's connection is redirected from the old source database to the new target database. After a period of monitoring to ensure stability, the old database can be decommissioned.
Database Schema Migration
A database migration isn't a single event but creates a carefully orchestrated project. To ensure data is moved securely, accurately, and with minimal disruption, the process is typically broken down into three main phases: thorough planning, active execution, and final validation.
The initial pre-migration phase is the most critical for success. It begins with a thorough assessment of the source database to understand its data, schema, and dependencies.
Teams then define clear business goals, choose a migration strategy (like a "lift-and-shift" or a phased approach), and select the right tools equivalent to the strategy. A key part of this stage is designing the target database's schema and, most importantly, backup solutions, performing a full backup of the source database to ensure a safe rollback path in case of any failures.
Next is the execution phase, where the data is actively moved for users. This typically follows an extract, transform, and load (ETL) model.
Data from each table and column is first extracted from the source database. Then, it undergoes transformation, which is especially crucial in heterogeneous migrations (moving between different database types). This step cleans, reformats, and remaps the data to fit the new database's structure. Finally, the transformed data is loaded into the target database.
After the data from each table and column is loaded, the post-migration phase begins. The team must rigorously validate the data to ensure no information was lost or corrupted during the transfer, often by comparing row counts and sampling data.
At the same time, when we migrate, applications are tested against the new database to confirm full functionality for users. Once all tests are passed, the team performs the final cutover, where the live application's connection is redirected from the old source database to the new target database. After a period of careful monitoring to ensure stability, the old database can be decommissioned.
Types of Database Migrations
While "database migration" is often used as a catch-all term, there are several distinct types, each with different goals and complexities.
Storage migration
This is the method of moving data from one physical or virtual storage medium to another. Examples include upgrading from on-premise hard drives (HDDs) to faster Solid-State Drives (SSDs) or moving data from an on-premise server to cloud-based object storage. The data format and structure typically remain the same for users.
Homogeneous migration
In this type, the source and target databases use the same underlying technology from the same vendor (e.g., migrating from an on-premise MySQL database to a cloud-hosted MySQL database). This is the most straightforward type of migration, as the schema and data types are already compatible.
Heterogeneous migration
This is the most complex type of change in migration. It involves moving data between two different database systems (e.g., migrating from an on-premise Oracle database to a cloud-based PostgreSQL database). This process requires a full transformation of the schema, data types, and functions to be compatible with the new target system.
Application migration
This type is driven by a change in an application. When a company switches from one software (like an old ERP) to a new one, the underlying data must be extracted from the old application's database and moved into the new application's database, which will have a completely different structure.
Finally, when we migrate, data consolidation of each table and column involves combining data from multiple, disparate sources into a single, unified target database. A common example is migrating data from several departmental databases (e.g., in marketing, sales, and finance) into a central data warehouse for unified business analytics.
Database Migration Strategies
Choosing the right strategy in change and migration is critical to a migration's success, as it dictates the timeline, risk, and impact on business operations. The main strategies revolve around the timing of the move and the level of transformation involved.
Big bang migration
This strategy involves moving the entire dataset from the source to the target in a single, scheduled event.
The process requires taking the source system offline (creating downtime), performing the full migration, and then switching the live applications to the target database. It's the fastest and simplest approach, but also the riskiest, as any failure during the migration can lead to significant downtime.
Trickle migration
A more cautious and complex approach where data is migrated in stages. The source and target systems run in parallel, and data is moved in small, manageable chunks.
This often involves setting up a data replication method to keep the target database in sync with any new data coming into the source. This strategy minimizes or even eliminates downtime, making it ideal for critical 24/7 systems, but it requires more planning and technical overhead.
Lift-and-shift (Rehosting)
This is a common strategy for cloud migrations. The database is moved from its on-premise server to a cloud-based server "as-is," with minimal or no changes to the database software or schema.
It's a fast way to modernize infrastructure and reduce hardware costs, but it doesn't take full advantage of new cloud-native database features.
Refactoring (Re-platforming)
This is the most complex change strategy and is often used during heterogeneous migrations. The database isn't just moved; it's fundamentally redesigned and optimized for the new target environment.
This might involve changing the schema method, normalizing data, and rebuilding applications to leverage cloud-native services. While it requires the most effort, it yields the greatest benefits in performance, scalability, and long-term cost savings.
Key Benefits of Database Migration
Migrating a database and each table and column is a significant undertaking, but it unlocks crucial technical and business advantages. Companies pursue these complex projects to gain a competitive edge, modernize their infrastructure, and improve the value of their data. The key benefits include:
- Cost reduction: Lowers expenses by moving from costly on-premise hardware and legacy software licenses to more efficient, pay-as-you-go cloud models.
- Improved performance and scalability: Modern databases, especially cloud-native ones, offer significantly faster processing, lower latency, and the ability to scale resources up or down instantly, a good reason to migrate.
- Enhanced security and compliance: Newer platforms provide a superior encryption method, advanced security controls, and more robust auditing features, making it easier to meet regulatory and disaster recovery requirements.
- Unified data and advanced analytics: Migrating allows for the consolidation of data from multiple silos into a single source, enabling powerful business intelligence, AI, and data analytics.
- Modernization and agility: Replaces outdated, unsupported legacy systems, reducing technical debt and allowing teams to build and deploy new applications faster.
Challenges and Risks of Database Migration
While the benefits are significant, a database migration is a complex undertaking fraught with technical and business risks. Careful planning is essential to navigate these challenges, as any oversight can lead to costly failures, data loss, or significant operational disruptions.
Data loss or corruption
This is the most critical risk. During the transfer, data can be lost, duplicated, or incorrectly transformed, leading to data integrity issues in the new system.
Downtime and business disruption:
Many migrations require taking the source database offline, at least for the final cutover. If this downtime is unplanned or extends longer than expected, it can halt business operations, impact revenue, and damage customer trust.
High complexity and cost:
Underestimating the project is common. Factors like complex legacy schemas, hidden data dependencies, and the need for data transformation in heterogeneous migrations can cause the project to run over budget and past its deadline.
Security and compliance gaps
Moving data exposes it to new vulnerabilities, both in transit and at rest. The migration team must ensure that strict security protocols, encryption, and access controls are maintained to comply with regulations like GDPR or HIPAA, avoiding potential breaches and fines.
Even if the data is moved successfully, the new database might not perform as expected. Poorly optimized queries, improper configuration, or application incompatibility can lead to a slow, inefficient system after the launch.
Best Practices for a Successful Migration
A successful database migration is a complex project that hinges on meticulous planning and a proactive approach to risk. To avoid common pitfalls like data loss, extended downtime, and budget overruns, it's crucial to follow a set of established best practices. These guidelines help ensure a smooth, secure, and accurate transfer from start to finish.
Define clear objectives and scope: Understand the business and technical goals of the migration (e.g., cost, performance, modernization) and clearly define what data is included.
Thoroughly audit the source: Perform a deep analysis of the source database, including its schema, data, dependencies, and any obsolete or "dark" data that can be cleaned up or left behind.
Create a full, verified backup: Before any data is moved, ensure you have a complete and restorable backup of the source database. This is your most critical safety net.
Test applications extensively: Move beyond just data validation. Conduct thorough performance testing and User Acceptance Testing (UAT) to ensure all applications function correctly and efficiently with the new database.
Develop and test a detailed rollback plan: Know the exact steps you will take to revert to the source database if the migration fails for users at any stage. Test this plan in a staging environment.
Monitor post-cutover performance: After the final switch, closely monitor the new database for any performance bottlenecks, query issues, or unexpected behavior.
Prioritize data validation: Create a comprehensive plan to test and validate data integrity. This includes running queries, checking row counts, and sampling data before, during, and after the migration to ensure nothing was lost or corrupted.
Ensure security and compliance: Encrypt all data, both in transit (as it moves) and at rest (in the new database). Enforce strict access controls and ensure the entire process meets regulatory requirements like GDPR or HIPAA.
Database Migration Tools and Solutions
No modern database migration is performed manually. Teams rely on a wide range of specialized tools and platforms to automate the process, reduce risk, and ensure data integrity. These solutions can be broadly categorized into native utilities, managed cloud services, developer frameworks, and specialized third-party platforms.
The most prominent tools today are the managed solutions offered by major cloud providers, which are designed to simplify moves into their ecosystems.
Beyond the major cloud platforms, many other tools fill specific roles. For application-driven migrations, developers often use built-in frameworks like Entity Framework (EF), core migrations, or open-source tools like Flyway and Alembic.
These tools allow schema changes to be managed and version-controlled alongside the application's code. Additionally, the migration process is critically supported by data protection software, such as Acronis True Image, which provides the essential backup and recovery capabilities needed for a safe rollback plan.
OVHcloud and Database Migration
Go beyond compute with a full suite of services for your infrastructure needs. Whether you're modernizing legacy applications, managing massive datasets, or offloading database administration, these solutions are built for performance and interoperability.
Cloud Databases: Power your applications with our fully managed database as a service (DBaaS) solutions. Focus on building and deploying your code while we handle the complex, time-consuming administrative tasks. Our experts manage the installation, updates, maintenance, backups, and security of your database infrastructure.
Cloud Storage Solutions: Store, secure, and manage your data with our comprehensive range of high-performance, scalable storage solutions. Whether you need to host unstructured data, manage enterprise files, power high-transaction databases, or archive critical data for the long term, we have the right solution for you.
Datacentre Extension and Migration: Seamlessly transition your on-premises infrastructure to the cloud with our datacentre extension and migration solutions. Whether you're looking to fully migrate and modernize legacy hardware or build a flexible hybrid cloud, our services provide the agility you need.