Effective Data Migration Strategies – Big Bang, Phased, Parallel Run

Data Migration is an essential part of any digital transformation. It will allow you to transfer your data to your new databases, cloud environments, and Enterprise Applications. Depending on what you’re looking to do (e.g. upgrading your ERP system, or updating your old software), having the Right Data Migration Strategy can make a big difference.

However, Data Migration should be done carefully so that accuracy is maintained, there isn’t too much disruption, and data is kept secure.
Common strategies include: Big Bang Migration, Phased Migration and Parallel Run Migration. All of which have benefits, challenges and requirements.

Why IT Matters to Choose the Right Data Migration Strategy

Using a poor Data Migration strategy can cause issues including:

• Missing data
• Confusing Data
• Down time
• Security issues
• Unexpected Costs

Choosing the Right Data Migration Strategy can:

• Reduce down time
• Ensure data is accurate
• Reduce risks
• Reduce costs
• Improve performance Depending on your data, system, resources, and how much down time you can afford, you will want to choose the correct strategy.

1. Big Bang Data Migration

Big Bang Migration means all of your data that you need is transferred during one migration window. Once the Data Migration has been done and verified, you can fully move across to the new environment.
This type of migration usually occurs at weekends, holidays or during scheduled maintenance.
The process includes, preparing the destination system, extracting data from the source, transforming and loading into the new system. Once verified, users will fully use the new system.
Benefits

• Fast – All data will be transferred in one go.
• Less Complex – You won’t have to run multiple systems.
• Less long term costs – There aren’t many temporary links needed.

• Clear date for changeover – Employees know when they will be moving to the new system.
  Challenges

• More risk at changeover – If there is a major issue during the migration, IT can all be impacted.

• Down time – There could be some business interruption.

• Less flexibility to roll back – If new transactions are done, IT can be difficult to switch back to the old system.

• More preparation – You’ll need to do testing, back up, verification and roll back planning.
  When to use Big Bang Migration
  This is best used if you have a manageable amount of data, predictable requirements and a system that can cope with some down time.
  If you have a small business and are updating your internal customer management system, you may want to do IT in one go.

2. Phased Data Migration

With phased Data Migration, data is transferred in chunks.
You can split your migration between departments, functions, locations, applications or specific sets of data.
For example, if you’re migrating your ERP system, you may want to migrate your financial data first, then your inventory, staff and customer data.
The process includes identifying different groups of data to migrate, and an order to migrate them in. Data is migrated, tested and verified. During the migration, the old and new systems may be running.
Benefits

• Less risk – Issues can be identified and resolved within each phase.
• Easier resource management – Resources can be divided between phases.
• Business isn’t impacted – Departments can be changed over.
• More testing – Each phase has been completed so you can get feedback.
• More flexibility – You can adapt your migration based on previous results. Challenges
• Longer time to complete – More phases to complete.
• Integration – Old and new systems may need to be temporarily linked.
• Synchronisation – You’ll need to ensure data is in sync.
• More coordination – Different teams will need to work together.

When to use Phased Migration

This is great for larger organisations who have complex applications, large amounts of data and many departments. For example, a multinational company may want to change over their legacy ERP platform. They can do this by changing each business unit individually. This also means if there are any unexpected issues, they can learn from previous phases.

3. Parallel Run Data Migration

Parallel Run Migration means you’ll run both your old and new systems at the same time.
You’ll run the same transactions or activities on both systems. This means you can verify that your new system is producing accurate outputs.
The process includes migrating your data across to the new system. Both systems will run the same business transactions. The migration team will compare the outputs. Any inconsistencies will be identified and resolved before approval.
For example, during your new payroll management system implementation, you can run your staff salaries on both systems. This will allow you to compare the calculations, deductions and payments to identify any discrepancies.
Benefits

• More confidence – You can compare the results of both systems.
• Accurate data – Any inconsistencies in your data can be identified.
• Less risk – Your old system will still be running whilst verifying.
• Better reliability – You can test the new platform in a real situation.

• Safer – You can delay your changeover until the new system meets your requirements.
  Challenges

• More costs – You will have to run both systems.

• Double work – Transactions may have to be done twice by employees or automation.

• Synchronisation – Both systems must keep information in sync.

• Longer time to complete – The systems will be running together.

• When to use Parallel Run Migration
  This is best used for any business processes that could cause serious issues if inaccurate. Industries such as Banking, Healthcare, Insurance and Financial Services can benefit from this when implementing key business applications.

4. Comparison of Data Migration Strategies

Understanding the differences between Big Bang, Phased and Parallel Run can help you decide which strategy to use.
Big Bang is usually best used for smaller or manageable migrations. You’ll have a downtime window and can complete the migration quickly. However, there is more risk at changeover and a lot of preparation needs to be done.

Phased is best used for larger organisations with complex applications, lots of data and many departments. You’ll be able to identify issues early, resources can be easily managed and any issues with the migration can be reduced. However, IT will take longer, more coordination and temporary integration.

Parallel Run is best used for key business applications. Both systems can be run at the same time meaning you can compare results, identify discrepancies and verify the new environment. The main downside is increased costs.

There is no right answer. It depends on your business requirements, technical capabilities, budget, timeline and acceptable risk.

5. How to Ensure a Successful Data Migration

Whatever strategy you decide on, you should follow these steps.
Step 1: Understand your current data
Identify what data sources you have, the structure of your databases, applications dependancies and how much data you need to migrate.
Identify if the data is of good quality. Are there duplicates, outdated, incomplete or confusing records?
Step 2: Define your objectives
Define your objectives, including when you want to migrate, how much down time you can allow, how accurate the data needs to be, security requirements and what you want to achieve.
This will help you decide which strategy to use.
Step 3: Clean your data
It’s important to clean your data to prevent any issues from impacting your new environment.
Remove any unnecessary data. Resolve any inconsistencies. Standardise any data and ensure the correct mapping rules are in place.
Step 4: Decide on the migration strategy
Understand the benefits and limitations of each of the three strategies.
Consider how your business will run, how complex your data is, your technical resources and your rollback requirements.
Step 5: Test
Do test migrations.
Verify that the number of records, financial figures, relationships, data and applications are correct. Ensure you do some realistic testing.
Step 6: Back up
Ensure you have reliable back up for your original environment. Have a rollback plan in place.
Decide when to stop the migration. Who will approve and/or roll back.
Step 7: Monitor
Monitor your new environment. Ensure everything is running well, data is accurate, applications are working and collect feedback. Ensure you have your old system running in read only for a suitable period of time (depending on your retention and compliance).

6. Common Mistakes to Avoid

Even businesses with experienced technical teams can face issues with their Data Migration. Common mistakes include:

• Not planning
• Not understanding your current infrastructure and data dependancies.
• Not considering data quality – Migrating inaccurate or duplicated data.
• Not testing – Not verifying the migrated data and applications.
• Not communicating – Not informing employees of the migration schedule.
• No rollback plan – Not having tested back up.
• Not considering security – Not putting in place access, encryption and data protection. To avoid these issues, ensure your IT team, business, project managers and data experts work together.

Conclusion

Choosing the Right Data Migration Strategy will help ensure your digital transformation is efficient, secure and reliable.

Big Bang will allow faster migration if you can allow for a downtime window. Phased gives you more flexibility if you have a large and complex environment. Parallel Run gives you more confidence as you can compare both systems.

Overall, IT’s important to plan, clean your data, test, verify and monitor.

When looking to update your infrastructure, ensure you carefully consider your business requirements and choose the best strategy for long term growth.

For more information on how to plan your migration, choose the right strategy, verify your data and more, take a look at our guide on effective Data Migration strategies by 4Labs Technologies.