GlobalTech Solutions, a multinational corporation, is undertaking a complex data migration project to consolidate customer data from several disparate legacy systems into a centralized, cloud-based data warehouse. These legacy systems, acquired through various mergers and acquisitions, each employ different data formats, validation rules, and data quality standards. The project aims to create a single, unified view of customer information to improve business intelligence and customer relationship management. As the Data Quality Lead, you are tasked with identifying the most critical aspect to monitor during the initial stages of the data migration to ensure the success of the project. Considering the challenges of integrating data from diverse sources with varying quality levels, which of the following should be prioritized to mitigate potential risks and ensure the integrity of the migrated data? Assume that basic security protocols, infrastructure scalability, and user access controls are already in place. The primary concern is now focused on the data itself.