What is Data Migration
In general, data migration is the process of moving digital information. These projects are often initiated due to various reasons, such as upgrading databases, deploying new applications, or migrating from on-premises to cloud-based environments. The migration process typically involves preparing, extracting, transforming, and loading the data, usually as a one-time effort.
Data Migration Types
Migration types refer to the various strategies used to move databases, storage, applications, business processes, and cloud environments. Common migration types are described below. The specific type of data migration undertaken depends on business requirements.

Database migration
Database migration can refer to either moving data from one database vendor to another, or to upgrading your database software to a newer version. The data format can vary between vendors so a transformation process may be required. In most cases, a change in database technology should not affect the application layer but you should definitely test to confirm.
Storage migration
Storage migration involves transferring data from an existing repository to another, often new repository. The data usually remains unchanged during a storage migration. The goal is typically to upgrade to more modern technology which scales data more cost-effectively and processes data faster.
Business process migration
Business process migration involves the transfer of databases and applications containing data related to customers, products, and operations. Data often requires transformation as it moves from one data model to another. These projects are usually triggered by a company reorganization, merger or acquisition.
Application migration
Application migration refers to moving a software application such as an ERP or CRM system from one computing environment to another. The data usually requires transformation as it moves from one data model to another. This process most often occurs when the company decides to change to a new application vendor and/or involves transferring from on-premises to a public cloud or moving from one cloud to another.
Cloud migration
Cloud migration is a frequently discussed aspect of data migration, encompassing the movement of data, applications, and other business components to a cloud computing environment, including cloud data warehouses. This migration can occur from an on-premises data center to a public cloud, or between different cloud platforms. The reverse process, known as “cloud exit,” involves migrating data and applications from the public cloud back to an on-premises infrastructure.
Common Data Migration Challenges
Due to the criticality of data to organizational operations, data migration is a complex process necessitating thorough risk assessment. Numerous challenges frequently arise during implementation. The following are some of the most common data migration challenges.

- Data Loss: Data Loss: Incomplete data transmission can occur. This can result in irrevocable data loss.
- Semantics errors: Data migration can lead to semantic errors, where the meaning or interpretation of data changes. For instance, if a source field called “grand total” is migrated to a different field or column in the target system, the data’s intended meaning is lost or distorted.
- Extended downtime: If the migration process takes longer than anticipated, it can lead to significant disruptions and losses for your business.
- Data corruption: Migrating unwanted data types can corrupt the target system. This can lead to system crashes or damage the data organization.
- Performance: Performance issues can stem from poor code quality, application bugs, or an inability to handle high workloads.
- Orchestration: Orchestration refers to the organized migration of disparate data from multiple sources to a unified location. Inadequate data migration planning can lead to the unintended creation of new data silos by failing to maintain proper tracking of data points. This issue is compounded when multiple disconnected teams operate within different departments or when functional and technical teams utilize data in a variety of ways.
- Integration: Integrating data sources with other tools and systems allows for data sharing. However, improper integration can lead to the loss of valuable insights.
- User training: Data migration necessitates a shift in staff focus from existing systems to a new platform. Without adequate training on the new system, users are more prone to making errors.
- Data security: Data migration introduces significant security risks, including potential exposure to third parties and the possibility of migrating to a more vulnerable system.
- Data quality: Poor data quality, including missing, inconsistent, useless, or incorrect data, can have significant negative consequences when migrated. These consequences include reduced target system performance, bugs, and system errors.
Not only above mentioned challenges, but business continuity and costs are common faced challenges.
- Business continuity: To ensure a positive user experience during data migration, minimize service disruption. When downtime or slowdowns are unavoidable, schedule migrations during off-peak hours and provide clear, timely communication to users through multiple channels, including email, in-app notifications, and social media.
- Costs: Data migration involves various expenses, including tools, human resources, new infrastructure, and decommissioning costs for old infrastructure. Thorough budgeting is essential before starting the process. Factor in potential productivity and revenue losses due to downtime. Minimizing outages and proactive user communication can help control migration costs.
Common migration strategy
Several common strategies are employed for data migration, which is the process of moving data between platforms. These include:
Big Bang data migration
In a Big Bang migration, all data assets are moved from the source environment to the target environment in a single, comprehensive operation within a relatively short window of time. This approach necessitates system downtime during the data transfer and transformation process to ensure compatibility with the target infrastructure.
Advantages: less costly, less complex, takes less time, all changes happen once
Disadvantages: a high risk of expensive failure, requires downtime
The big bang approach fits small companies or businesses working with small amounts of data. It doesn’t work for mission-critical applications that must be available 24/7.
Trickle migration
Trickle Migration (also known as phased or iterative migration): This strategy divides the overall migration process into smaller, manageable sub-migrations, each with its own specific objectives, timelines, scope, and quality assurance measures. By operating the old and new systems concurrently and migrating data in small increments, trickle migration achieves near-zero downtime, maintaining uninterrupted application availability for users.
Advantages: less prone to unexpected failures, zero downtime required
Disadvantages: more expensive, takes more time, needs extra efforts and resources to keep two systems running
Trickle migration is the right choice for medium and large enterprises that can’t afford long downtime but have enough expertise to face technological challenges.
Comparison of Migration strategy
Feature/Aspect | Trickle Migration | Big Bang Migration |
Definition | Data and systems are migrated incrementally, in smaller phases, over time. | All data and systems are migrated in one large, single event. |
Approach | Iterative and gradual. | One-time, all-at-once migration. |
Timeline | Extended, as it spans multiple phases or iterations. | Shorter, focused on a single migration window. |
Risk | Lower risk due to phased testing and gradual changes. | Higher risk because everything changes at once. |
Complexity | More complex due to managing coexistence of old and new systems. | Simpler as there’s no coexistence of systems. |
Downtime | Minimal downtime per phase, but over a longer time overall. | Typically involves a significant downtime window. |
Testing | Easier to test in smaller chunks. | Requires comprehensive pre-migration testing. |
User Impact | Lower immediate impact, users can transition gradually. | High immediate impact, users must adapt quickly. |
Cost | Potentially higher due to prolonged migration and dual operations. | Lower due to single-event focus but risks unforeseen costs from errors. |
Suitability | Best for large, complex systems with critical operations needing minimal disruptions. | Best for smaller, less complex systems or when speed is a priority. |
Migration Process
Data migration projects, due to their involvement with critical data and potential impact on stakeholders, present inherent challenges. Prior to any data transfer, a robust and well-defined migration plan is a necessity. A successful data migration initiative is predicated on an initial, comprehensive analysis and assessment of the data’s lifecycle. Irrespective of the specific methodology employed, all data migration projects adhere to a consistent set of key phases.

Stage 1: Project Planning
Prior to commencing the migration process, it is imperative to establish well-defined objectives and delineate the scope of the data migration. This process involves determining the precise data set required for transfer, including the identification and exclusion of obsolete records. Furthermore, potential compatibility issues between the source and target environments must be addressed, particularly in cases involving migration between disparate database paradigms, such as from a relational database (e.g., Oracle) to a non-relational database (e.g., MongoDB).
This initial phase involves follow key steps:
1.1. Define clear and measurable objectives
Define clear and measurable objectives for the data migration project, including specifying the precise data to be migrated, defining success criteria.
1.2. Refine the project scope
Define the precise scope of the data migration by identifying and excluding all non-essential data elements, focusing solely on the minimum dataset necessary to ensure effective target system operation. This process necessitates a high-level comparative analysis of the source and target systems, conducted in consultation with the end-users directly impacted by the migration.
1.3. Risk assessment
A comprehensive risk assessment is conducted to identify potential challenges and roadblocks that could impede the data migration project. This assessment includes evaluating potential impacts on the organization and developing mitigation strategies for contingencies such as data loss, downtime, or other failures.
1.4. Estimate the budget and set realistic timelines
Subsequent to scope refinement and system evaluation, the appropriate migration methodology (e.g., Big Bang or Trickle) is selected, resource requirements are estimated, and a realistic project timeline is defined. It should be noted that enterprise-scale data migration projects typically require a duration of six months to two years.
Stage 2: Discovery and Profiling
This initial phase of the data migration methodology involves a comprehensive assessment of the data landscape. This assessment encompasses data inventory, analysis, auditing, and profiling to thoroughly examine and cleanse the data set targeted for migration. The objective is to identify and address potential data conflicts, detect and remediate data quality issues, and eliminate redundant or anomalous data elements prior to the commencement of the migration process.
2.1. Source System Assessment
2.1.1. Identify Data Sources
- Primary Sources: Identify the primary sources of data, such as databases, files, APIs, etc.
- Secondary Sources: Identify any secondary or external data sources that may need to be migrated.
2.1.2. Understand the Data Structure
- Data Models: Review the data models, schemas, and relationships between different data entities.
- Data Types: Identify the types of data (e.g., text, numeric, date, binary) and their formats.
- Data Volume: Estimate the volume of data to be migrated, including the number of records, tables, and databases.
- Data Quality: Assess the quality of the data, including issues like duplicates, missing values, and inconsistencies.
2.1.3. Analyze Data Dependencies
- Interdependencies: Identify relationships and dependencies between different data entities.
- Business Rules: Understand any business rules or logic applied to the data in the source system.
- Data Flow: Map out how data flows through the source system, including ETL (Extract, Transform, Load) processes.
2.1.4. Evaluate Data Security and Compliance
- Access Controls: Review who has access to the data and what permissions they have.
- Encryption: Check if data is encrypted at rest or in transit.
- Compliance: Ensure the data complies with relevant regulations (e.g., GDPR, HIPAA).
2.1.5. Document Source System
- Metadata: Document metadata, including data definitions, formats, and constraints.
- Data Dictionary: Create or update a data dictionary that describes the data elements in the source system.
2.2. Target System Assessment
2.2.1. Understand the Target System Architecture
- Data Models: Review the data models and schemas of the target system.
- Data Types: Ensure the target system supports the data types and formats used in the source system.
- Storage Capacity: Verify that the target system has sufficient storage capacity for the migrated data.
2.2.2. Evaluate Data Transformation Requirements
- Data Mapping: Map data fields from the source system to the target system.
- Data Transformation: Identify any transformations needed to convert data from the source format to the target format.
- Data Validation: Plan for data validation to ensure accuracy and completeness after migration.
2.2.3. Assess System Performance
- Performance Benchmarks: Evaluate the performance of the target system to ensure it can handle the volume and complexity of the migrated data.
- Scalability: Ensure the target system can scale to accommodate future data growth.
2.2.4. Review Security and Compliance
- Access Controls: Ensure the target system has appropriate access controls in place.
- Encryption: Verify that data will be encrypted at rest and in transit in the target system.
- Compliance: Ensure the target system complies with relevant regulations.
2.2.5. Test the Target System
- Test Environment: Set up a test environment that mirrors the target system.
- Pilot Migration: Perform a pilot migration to test the process and identify any issues.
- User Acceptance Testing (UAT): Conduct UAT to ensure the migrated data meets user requirements.
2.3. Comparative Analysis of Source and Target Systems
2.3.1. Network and Connectivity
- Confirm bandwidth, latency, and reliability between source and target systems.
- Address firewall or VPN requirements for data flow.
2.3.2. Data Transformation Needs
Determine if data needs cleansing, enrichment, or reformatting during migration.
Plan for ETL (Extract, Transform, Load) processes if required.
2.3.3. Testing Environments
Establish sandbox or test environments in both systems for validation.
2.3.4. Documentation and Communication
Document findings and share with stakeholders to align expectations.
Maintain clear communication between teams managing source and target systems.
Stage 3: Resource Allocation and Solution Development
For large data assets, a phased development approach is recommended, wherein the data is segmented, and the migration logic is developed and tested iteratively for each segment.
3.1 Set data standards
This will allow your team to spot problem areas across each phase of the migration process and avoid unexpected issues at the post-migration stage.
3.2 Architecture Design and Resource Allocation
This phase encompasses both the design of the migration architecture and the allocation of necessary resources. It is imperative to confirm the availability and commitment of all requisite resources, including internal personnel, external consultants, vendors, and enabling technologies. This verification extends to resources required for post-migration activities, such as user training and communication. Upon confirmation of resource availability, the development of the migration logic commences, encompassing the processes of data extraction, transformation, and loading (ETL) into the designated target repository.
3.3 Create a Detailed Migration Plan
- Data Extraction: Plan for data extraction from the source system.
- Data Transformation: Outline the steps for data transformation.
- Data Loading: Plan for loading data into the target system.
- Testing: Include testing phases in the migration plan.
stage 4: Backup and Contingency Planning
Despite careful planning, data migration projects can face unexpected challenges. A robust backup strategy is essential to ensure data can be recovered and systems remain operational in the event of unforeseen issues during the migration process. Furthermore, detailed contingency plans should be developed to address each identified potential setback or roadblock.
stage 5: Execution
5.1. Pre-migration – sampling testing
To assess the accuracy of the migration and identify any potential data quality issues, test the migration process using a representative data sample.
5.2. User Acceptance Testing (UAT)
User Acceptance Testing (UAT) is a critical phase in the data migration process where end-users validate that the migrated data and system meet their business requirements and expectations. UAT ensures that the migration solution works as intended in a real-world scenario before it is fully deployed. we should focus on business goals and customer satisfaction.
5.3. Executing the Migration Solution
Following successful completion of testing procedures, the data migration process, encompassing data extraction, transformation, and loading (ETL), is formally initiated. In a Big Bang migration scenario, the execution phase is typically completed within a period of several days. Conversely, the Trickle migration methodology employs an incremental data transfer approach, resulting in a more protracted execution timeline but significantly mitigating the risk of critical system failures and minimizing downtime.
stage 6: Documentation and Reporting
After completing a data migration, documentation and reporting are critical steps to ensure the process is well-documented, auditable, and provides insights for future improvements. Proper documentation and reporting help stakeholders understand the migration’s success, identify any issues, and maintain a record for compliance and reference purposes.
6.1. Documentation
Documentation provides a detailed record of the data migration process, including the steps taken, decisions made, and outcomes. It serves as a reference for future migrations, audits, or troubleshooting.
Key Components of Documentation
- Migration Plan:
- Include the original migration plan, including objectives, scope, timelines, and resource allocation.
- Data Mapping:
- Document the mapping of source data fields to target data fields.
- Include any transformations or conversions applied during the migration.
- Data Validation:
- Record the validation rules and checks performed to ensure data accuracy and completeness.
- Include sample validation results and any discrepancies found.
- Error Handling:
- Document any errors encountered during the migration and how they were resolved.
- Include a log of rejected or failed records and the reasons for rejection.
- Migration Tools and Scripts:
- Provide details of the tools, scripts, or software used for the migration.
- Include version numbers, configurations, and any custom code.
- Testing Results:
- Document the results of pre-migration testing, including unit tests, integration tests, and user acceptance tests (UAT).
- Include test cases, expected outcomes, and actual results.
- Post-Migration Verification:
- Record the steps taken to verify the success of the migration.
- Include checks for data integrity, completeness, and performance in the target system.
- Lessons Learned:
- Summarize what went well and what could be improved in future migrations.
- Include feedback from the migration team and stakeholders.
- Compliance and Security:
- Document compliance with relevant regulations (e.g., GDPR, HIPAA).
- Include details of security measures taken during the migration.
- Rollback Plan:
- Document the rollback plan and whether it was executed (if applicable).
- Include details of any fallback procedures used.
6.2. Reporting
Reporting provides a summary of the migration process and outcomes for stakeholders. It highlights key metrics, successes, and areas for improvement.
Key Components of Reporting
- Executive Summary:
- Provide a high-level overview of the migration, including objectives, scope, and outcomes.
- Highlight key achievements and challenges.
- Migration Metrics:
- Include quantitative metrics such as:
- Volume of data migrated (e.g., number of records, tables, databases).
- Time taken for the migration.
- Number of errors or rejected records.
- Downtime (if applicable).
- Include quantitative metrics such as:
- Data Quality Report:
- Summarize the results of data validation and quality checks.
- Include metrics such as:
- Percentage of accurate records.
- Percentage of incomplete or duplicate records.
- Number of records requiring manual intervention.
- Performance Report:
- Compare the performance of the target system before and after migration.
- Include metrics such as:
- Response times.
- Throughput.
- System uptime.
- Issue and Risk Log:
- Provide a summary of issues encountered during the migration and how they were resolved.
- Include a risk assessment and mitigation strategies.
- Stakeholder Feedback:
- Summarize feedback from stakeholders, including end-users, IT teams, and business leaders.
- Highlight any concerns or suggestions for improvement.
- Post-Migration Support:
- Document the support provided after the migration, including:
- Troubleshooting and issue resolution.
- User training and documentation.
- Monitoring and maintenance activities.
- Document the support provided after the migration, including:
- Recommendations:
- Provide recommendations for future migrations or system enhancements.
- Include best practices and lessons learned.
stage 7: Post-Migration Assessment Validating, Auditing and Monitor
7.1. Post-migration Validation and Auditing.
Once the migration is complete, perform post-migration validation to verify that all data is accurately transferred and that the new system functions as expected. Conduct regular audits to ensure data integrity and compliance with data regulations.
7.2. User Training and Communications
User Training and Communications, Ongoing stakeholder communications is crucial throughout the data migration process. This should include keeping everyone informed about the migration schedule, potential disruptions, and expected outcomes, as well as providing end-user training/instructions to smooth the transition and prevent any post-migration usability issues.
Once the migration is complete, perform post-migration validation to verify that all data is accurately transferred and that the new system functions as expected. Conduct regular audits to ensure data integrity and compliance with data regulations.
7.3. Continuous Performance Monitoring
Ongoing monitoring of the new system’s performance is vital for surfacing any post-migration data loss and/or data corruption issues. Regularly assess the target system’s performance and investigate any potential data-related performance bottlenecks/issues.
7.4. Data Security and Compliance
Last but certainly not least, ensure that data security and compliance requirements are met during and after the migration process. This may include implementing data encryption at rest and in transit, access controls, and data protection measures to safeguard sensitive information.
Conclusion
Assessing the source and target systems is a foundational step in ensuring a successful data migration. By thoroughly evaluating both systems, identifying potential risks, and developing a comprehensive migration plan, you can minimize disruptions and ensure that the migrated data is accurate, secure, and compliant with relevant regulations.
Sticking to the best practices can increase the likelihood of successful data migration. each data migration project is unique and presents its own challenges, the following golden rules may help companies safely transit their valuable data assets, avoiding critical delays.
Use data migration as an opportunity to reveal and fix data quality issues. Set high standards to improve data and metadata as you migrate them.
Hire data migration specialists and assign a dedicated team to run the project.
Minimize the amount of data for migration.
Profile all source data before writing mapping scripts.
Allocate considerable time to the design phase as it greatly impacts project success.
Don’t be in a hurry to switch off the old platform. Sometimes, the first attempt at data migration fails, demanding rollback and another try.
Data migration is often viewed as a necessary evil rather than a value-adding process. This seems to be the key root of many difficulties. Considering migration an important innovation project worthy of special focus is half the battle won.
Please do not hesitate to contact me if you have any questions at William . chen @ mainri.ca
(remove all space from the email account 😊)