A computer-implemented method for operating a legacy platform and a replacement platform in parallel during a dual operation phase of a migration of a data processing system from the legacy platform to the replacement platform, the method comprising: receiving, from an external source (12, 14, 16, 18, 20) input data at the legacy platform through a legacy input data feed, the input data relating to a first document in a legacy database; updating, by the legacy platform, the first document in the legacy database based on the input data; receiving, from the external source (12, 14, 16, 18, 20), the same input data relating to the first document at the replacement platform through a replacement input data feed; generating, by the replacement platform, a second document in a replacement database based on the input data; capturing, by the replacement platform, a first image of the second document in a first envelope in the replacement database, the first image in the first envelope conserving the generated second document at a specific point in time, the first envelope maintaining a history of the second document by adding an image of the second document to the first envelope when the second document is modified; migrating the first document from the legacy database to the replacement database; capturing, by the replacement platform, a second image of the first document in a second envelope in the replacement database, the second image in the second envelope conserving the migrated first document at a specific point in time, the second envelope representing the first document migrated from the legacy database; comparing the first image in the first envelope to the second image in the second envelope; and in response to the second image matching the first image, validating the second document in the replacement database. receiving, from an external source (12, 14, 16, 18, 20) input data at the legacy platform through a legacy input data feed, the input data relating to a first document in a legacy database; updating, by the legacy platform, the first document in the legacy database based on the input data; receiving, from the external source (12, 14, 16, 18, 20), the same input data relating to the first document at the replacement platform through a replacement input data feed; generating, by the replacement platform, a second document in a replacement database based on the input data; capturing, by the replacement platform, a first image of the second document in a first envelope in the replacement database, the first image in the first envelope conserving the generated second document at a specific point in time, the first envelope maintaining a history of the second document by adding an image of the second document to the first envelope when the second document is modified; migrating the first document from the legacy database to the replacement database; capturing, by the replacement platform, a second image of the first document in a second envelope in the replacement database, the second image in the second envelope conserving the migrated first document at a specific point in time, the second envelope representing the first document migrated from the legacy database; comparing the first image in the first envelope to the second image in the second envelope; and in response to the second image matching the first image, validating the second document in the replacement database.