Create one onBefore transform map script to copy the sys_id of new records from the source to the target instance. Create a second onBefore transform map script to identify records on the target instance that have the same unique values but different sys_id values.

Before you begin

Role required: admin.

Procedure

  1. Open the table transform map record you created.
  2. In the Transform Scripts related list, click New.
  3. In the When field, select onBefore.
  4. Enter the following script: 
    if (action == "insert") {target.setNewGuidValue(source.u_sys_id); }
  5. Click Submit.
  6. In the Transform Scripts related list, click New.
  7. In the When field, select onBefore.
  8. Enter the following Script: 
    /** 
* This script queries for a uniquely identifying value of the referenced record and then 
* updates the target reference field with the sys_id of the matching target record.
* This sample assumes:
* 1) The target table contains an assigned_to field which is a reference field.
* 2) The reference field references the User [sys_user] table.
* 3) You can use the email field to uniquely identify users. Alternatively you
*    could use the user_name field.
*/
var ref = new GlideRecord("sys_user"); //Replace sys_user with any reference table
ref.addQuery("email", source.email); //Replace email with any unique field
ref.query();
if(ref.next()){
   target.assigned_to = ref.sys_id; //Replace assigned_to with any reference field
}
  9. Click Submit.