When doing a direct path load the database has two different basic strategies, temp segment merge and brokered load.
https://blogs.oracle.com/optimizer/space-management-and-oracle-direct-path-load
There is a hint to enable brokered load (HWM_BROKERED ) but there is no hint to switch it off.
There is no hint to enable temp segment merge.
For some highly parallel inserts temp segment merge is the best strategy. If the inserts grows the segment quickly, brokered load can result in "enq: HV contention" waits.
The only way brokered load can be switched off is the hidden parameter "_INSERT_ENABLE_HWM_BROKERED" on system level.
This option is almost useless, because HWB is the better overall stategey. Only for some selected statements TSM is perferrable.