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 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 , 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 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 , 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 . <EOS>