Data Migration Series: How to approach a data migration?

Most data migrations can be pigeonholed into one of the two following categories. Those which take a ‘big-bang approach, and those that take a phased approach. How do decide on the right one?

6 minutes read | by Lee Smith | 22 December 2021

As previously stated in the first of our Data Migration blog series, data migrations are difficult. Actually, they are not just difficult, they are very difficult. But why? Afterall, data migrations are just the process of moving data from one place to another. One of the key elements is deciding on which data migration approach to take.

Effectively, there are two main approaches for data migration projects. Each of these have their own nuances, but making the decision on which path to take, well ahead of the project starting is key.

So, what are these two main approaches?

Most data migrations can be pigeonholed into one of the two following categories. Those which take a ‘big-bang approach, and those that take a phased approach.

Let’s take a look at these data migration approaches in more detail.


What is a Big-bang Migration?

A Big-bang data migration is when all of the data is moved in one main phase. Generally, this will occur when there is a planned date for older systems to be switched off. All the data will be prepared and ready for the final migration and then a small-time window will be allocated for the transfer of the data. From that point onwards your new systems will be live.

This particular approach is time-sensitive and high-pressured, but there are some key benefits to consider when taking this approach. One such benefit is that users have a single point in time when they are expecting the transition to occur. This avoids confusion on where they are expected to access and process the data used in their day-to-day routines.

Another key benefit to big-bang data migrations is the minimal amount of down-time required. This is due to a small time window being allocated to the actual migration.

Often, big-bang migrations are less costly than phased migrations, as the legacy and new systems are not required to run in parallel for extended periods of time which greatly reduces support and licensing costs.

There are, however, a few challenges to be aware of if this is the desired approach. These can result in poor customer experiences, staff dissatisfaction, system failures and outage. Understanding these challenges will help minimise the potential impact on the overall project.

For more information on the how to address the challenges with big-bang migrations, please download the PhixFlow Data Migration Approaches guide.


What is a phased migration?

A phased migration is where you have a series of mini go live dates for each phase of the project. Essentially, the migration is broken down into smaller chunks. This will mean that you are running multiple systems in parallel, until all the data had been moved across and reconciled.

So, what are the benefits?

This approach allows core IT users and early adopters, within your business, to move to the new systems allowing for testing ahead of widespread adoption. This allows for a shallow learning curve, as users have more time to familiarise themselves with the new system before it is used extensively.

Another key benefit is the reduction in downtime required over the big-bang approach. As the data is migrated incrementally any downtime required is short and can be scheduled to run when the systems have minimal usage.

Phased migrations are also less prone to expensive errors. This is due to the data being processed in smaller chunks at any one time. Any errors that do occur will be rectified much quicker and changes to the logic can be made for future phases.

All good so far!

However, much like big-bang migrations, phased migrations do have their challenges too.

As we have already mentioned, phased migrations mean that multiple systems will be running in parallel. Often this leads to confusion on which system holds the most up-to-date data. Potentially, this can lead to poor customer service or giving the customer the wrong information.

Multiple systems also present the problem of differing functionality. This results in the customers experience is dependent upon which system their data currently resides on.

For more information on the how to address the challenges with phased migrations, please download the PhixFlow Data Migration Approaches guide.


Assess the potential risk to your business

So how do you decide on which data migration approach is right for you and your business?

Ultimately, your decision on which approach will work best for you should be based on the potential risk to the business. Which is the most cost effective? Which will minimise the load on the team, to maintain the day-to-day operation of the business? How are customers be affected? Are there any financial implications?

Whether you decide on a Big-bang approach or a Phased approach, the solution should always be designed to take all the data from the source system and put it in the target system, error-free, regardless of the timeframe.


How PhixFlow approach data migrations

At PhixFlow, we are here to help ensure your data migration project is a success. We do this by combining our professional services team with our data migration solution built on the PhixFlow Low-Code platform.

Our consultants have decades of expertise in data migration and have honed our skills through innovation and a wide variety of migration projects, across multiple industries and countries.

Our purpose-built data migration solution helps support your project, alleviating stress and overcoming challenges. The simplicity in which the PhixFlow Low-Code platform can be configured is one of its greatest strengths. PhixFlow enables you to fetch data from any source, profile that data and automate cleansing, corrections, and transformations, with confidence.

These abilities increase consistency and confidence in the data migration through:

  • Automated audit trail
  • Clear and precise understanding of the current state of the data
  • Interactive reporting and visualisations
  • Embedded data quality and governance processes
  • Decisions and estimates are based on accurate and current information
  • Optimised staff effectiveness
  • The need for re-work is minimised or eliminated
  • Projects are delivered on time and to budget

To ensure project success we follow our proven methodology, which works equally well for Big-bang or Phased migrations.

For more information, download the PhixFlow Data Migration Approaches guide.



Choosing how to perform a data migration may not always be easy. There are risks and benefits to both Phased and Big-bang migration. PhixFlow can help your company succeed at either data migration approach, ensuring you get the most out of your project. We are able to:

  • Automate processes
  • Reduce costs
  • Deliver on-time and on-budget
  • Encourage business engagement
  • Visualise your data at every step
  • Create supporting applications

For more information, or a demonstration, on how PhixFlow supercharge your data migration project, please contact us on or call +44 (0)1223 421030

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