Boris,
Options - All three but mainly Option # 2.
Option # 1 - To dynamically increase the number of parallel process from Source system. But in case of homogeneous system copies with massive database sizes, the database proprietary methods comes in handy than the R3load procedures.
Option # 2 - To reduce downtime in migrations (hetero combinations) thru parallel export/import of data loads.
Hope it helps.
Regards,
Srinivas K.