enq: TM-contention

 I have such problem:

I want to drop partition p1 from table REP_I. This table is parent for table REP_FL, and child for ~10 another tables.

Before I issue alter table REP_I drop partition p1, I removed rows from REP_FL which correspond to p1 (FK without option on delete cascade). 

Then I need to delete rows from REP_I .p1

When I issue delete from REP_I partition p1, my session is locked with another session.

Both have wait enq: TM-contention. My session wants to lock table REP_FL in mode 4 (request=4  - share (S)), and session which locks me has lock on REP_FL  in mode 3 (lmode=3 row-X (SX))