The Need for Data Migration
Healthcare organizations frequently migrate data between systems during EHR implementations, mergers and acquisitions, or system upgrades. Successful migration requires careful planning to preserve data integrity, maintain clinical continuity, and satisfy legal record retention obligations for information residing in legacy systems.
Source-to-Target Mapping
Source-to-target mapping documents how each data element in the legacy, or source, system corresponds to a field in the new, or target, system. This mapping process often reveals discrepancies in data structure, terminology, or granularity between systems that must be resolved before migration, such as a source system using free-text allergy fields while the target system requires structured, coded allergy entries.
Key Mapping Considerations
- Identifying equivalent fields and data types between systems
- Resolving terminology or code set differences, such as mapping legacy codes to standardized vocabularies
- Determining how to handle fields that exist in one system but not the other
- Establishing rules for historical data that predates current documentation standards
ETL Processes
Extract, Transform, and Load, commonly abbreviated ETL, describes the technical process of migrating data. Extraction pulls data from the source system, transformation converts and reformats the data according to the mapping specifications, and loading inserts the transformed data into the target system. Each stage requires validation to confirm data was correctly extracted, transformed, and loaded without corruption or loss.
Data Conversion Approaches
Organizations may choose a full conversion, migrating all historical data into the new system, or a hybrid approach that migrates only a limited dataset, such as active problem lists and recent encounters, while archiving the remaining legacy data for reference access. Full conversion offers seamless continuity but is more resource-intensive and carries greater risk of introducing errors into the new system.
Testing
Migration testing should include verification of a sample of migrated records against source system data, reconciliation of record counts between source and target systems, and user acceptance testing by clinical and administrative staff to confirm migrated data displays correctly and supports normal workflows.
Legacy System Decommissioning
Once migration is validated and the organization transitions fully to the new system, legacy systems must eventually be decommissioned. Before decommissioning, organizations must ensure continued access to any data not migrated, satisfying retention requirements, often through a read-only archive or a dedicated legacy data viewer accessible for the remainder of the applicable retention period.