In your job execution script, you can specify the scope of records to unmerge by setting IN_UNMERGE_ALL_XREFS_IND.
IN_UNMERGE_ALL_XREFS_IND=0: Default setting. Unmerges the single record identified in the specified XREF to its state prior to the merge.
IN_UNMERGE_ALL_XREFS_IND=1: Unmerges all XREFs to their state prior to the merge. Use this option to quickly unmerge all XREFs for a single consolidated record in a single operation.