A data processing method comprises receiving a request to perform a prior period adjustment (PPA) for a tenant in which data values applicable to a time period earlier than a current time period will be modified, in response to the request, identifying a working subset of data from tenant data in the production database and copying the working subset to a calculation database separate from the production database, performing the PPA, using the working subset in the calculation database, to result in creating and storing a plurality of result data, receiving, while performing the PPA, an additional request using the tenant data in the production database, performing the additional request using the tenant data in the production database while performing the PPA and updating the replay log, after completing the PPA and using the replay log, transferring the plurality of results to the production database.