A well managed data migration will ensure only the required information will be moved across to the new system or process. Validation and ownership must be put in place where the business owners sign off on the data when taking it over. A stakeholder must take on responsibility of the data. Because of this, communication is a key element of a successful data migration project.
Extract Skype's general ledger held on eBay's ERP system. The data had to be complete, balanced and validated by stakeholders in both Skype and eBay for accuracy and completeness. The number of transactions far exceeded Excel's capacity of 65,000 rows at the time so Excel had to process text files that held the data.
Create macros on Excel to process comma separated (csv) files. The macros had to summarize these files in order to validation tests in place and for final signoff. This was then joined into a larger process of overall validation of the data which had to be handed over to the business owners.
A well documented end to end process that showed the steps involved including business ownership and validation of data, provided confidence that all the relevant data had been extracted.