Converting data from a Legacy System to ERP


The purpose of this document is to outline a course of actions to cleanse data in the legacy system, or in a corresponding “staging area”, before it is loaded into a new ERP system.  Data conversion is one of the major reasons for an ERP project missing its go-live objective, and/or budget. These are general guidelines, which will need to be customized for each conversion when detailed cleansing instructions are rolled out.

Planning and execution in this phase are crucial.  Data quality pertains to issues such as:

  • Accuracy
  • Integrity
  • Completeness
  • Uniformity

Identify the data to be converted

It’s important to keep in mind that just because data can be converted, doesn’t necessarily mean it should be converted. An example might be a sales rep file.  If there are relatively few reps, for example, they can be entered directly into the new system.  Not only will this save the conversion charges, but there is a good chance each rep would need to have been edited anyway to change or add something.  There are probably reps no longer active anyway.  It will also allow users to become more familiar with the new system.

Decide what you really need. An enterprise software implementation is a great opportunity to “clean house.”

Types of data files

Master files like customer, vendor, and item

Transaction files like customer orders, purchase orders, and manufacturing orders

Historical files like sales analysis

Data preparation

Process owners need to take responsibility for the data. This is another critical step in a conversion strategy.  This is a perfect time to purge inactive customer, items, etc.  Often, process owners will say that their files are “pretty clean”.  As tempting as that may be to believe, it may be a euphemism for not having time to check everything.

Conversion timing

Converting the files to live too soon will cause file maintenance to be performed on both systems until go-live. This will generate a lot of extra work for little benefit. By all means do a practice conversion so that the process is ready to go. You will need the files for the conference room pilot anyway.

Converting the files to live too late will, obviously, compromise the go-live schedule. The General Ledger chart-of-accounts file should be converted, or entered, first, because nothing can be set-up or processed on the new system until it has been finalized and is in place.


Data Cleansing

Almost any application contains “dirty” data which will require “cleansing”.  This may involve automated data cleansing, manual data cleansing, or a combination of both.  Some causes for faulty data are:

  • Data that is meaningless
  • Is no longer representative of the business in which it is used
  • Contains some obvious human errors
  • Legacy systems often cause users to “fudge” data to work around software deficiencies
  • Will become meaningless in the new ERP environment
  • Differences in data models between the source and the target systems (lengths, decimal places, etc.)

All systems contain some “dirty” data, and conversion is the best time to rectify the situation.


Testing is a crucial step because if there are any issues at “go-live” 100% of the time spent resolving the issues and reconverting, is “downtime”.  The best way to handle this is to convert all of the data to your “conference room pilot” sandbox.  As users are learning the system, they will be testing the data conversion.

The following criteria should be considered while performing data integrity and conversion integration testing:

  • How many records did we expect to create?
  • Did the correct number of records get created? If not, why?
  • Has the data been loaded into the correct fields?
  • Is the data load complete – or are certain fields missing?
  • Has the data been formatted correctly?
  • Are balances correct?
  • Are any post-migration clean-up tasks in order?

The goal of a successful data migration is to keep the length of the deploy phase to a minimum. What is acceptable depends upon the organization – some will want this phase to last no more than a day, or less, others can tolerate a deployment that lasts a few days if availability is not a major concern.

Change management


One of the important functions of change management process is the communication of scope, purpose, and progress of the ERP project across the organization. This may be in the form of newsletter. The newsletter should include up to date news of the project, upcoming milestone, individual and group achievements, and should highlight benefit of the project. Also important are face-to-face meetings, workshops, teleconferences, etc.

The Human Factor

This is often overlooked, but it is a critical element of any successful technology initiative. Working hands-on with staff to ensure familiarity with the software as well as any changed roles, responsibilities or processes, is important to increase both employee buy-in and overall operational productivity. Resistance to change is usually encountered from employees in direct proportion to their length of service with the business. They may also be concerned about being replaced by the new system. They also know the outgoing legacy system very well, and are not yet familiar with the new system.  They may perceive it as their expertise slipping away. User buy-in of the ERP system is a critical success factor, and there is always difficulty in adapting to a new culture of computerized environment. Recognizing such behavioral issues and developing a plan to address, is one of the most important responsibility of the change agent.


User understanding of the new system is imperative, and organizing multiple and ongoing training sessions is an important function of the change management process. Training might include classroom training, workshop, hands on practice, streaming video, etc. A Procedures Manual with screenshots is very useful in any training program, and augments the effectiveness of the training.  In fact, asking users to create a manual of their function, including screenshots, is a good way to improve their confidence, and create buy-in to the new system. Make sure to help with and approve their efforts.

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