ADT/ACK - Merge visit - visit number

An A42 event is used to signal a merge of records for a visit that was incorrectly filed under two different visit numbers. The _incorrect source visit number_ identified in the MRG segment (MRG-5 - Prior Visit Number) is to be merged with the required _correct target visit number_ identified in the PV1 segment (PV1-19 - Visit Number). The _incorrect source visit number_ would then logically never be referenced in future transactions. It is noted that some systems may still physically keep this _incorrect identifier_ for audit trail purposes or other reasons associated with database index implementation requirements.