When a Data Connector Import Rule imports new associations or reverse associations to a one to many association, such as Software Purchases, prior associations to that record are removed.
For Data Connector 7.1, this is working as designed. There is no method of configuring associations or reverse association in an Import Rule to keep the prior associations.
For Data Connector 7.5, the ability to append associations or reverse associations has been added as a new feature.
For future versions, a feature request (Etrack 3634807) has been requested to add the ability for the user to be able to pick whether they manually want to append or overwrite. For 7.5 customers, the workaround is to first create a CMDB rule that uses <Clear> for the association, then run the import rule to replace them.
Upgrade to Symantec Management Platform 7.5 for this functionality.
For Symantec Management Platform 7.1, workarounds include:
Data Connector Import Rule fails to set a foreign key correctly