Drop Foreign Key and Insert causing deadlock

I run into deadlock when one session is dropping Foreign key from a table while other session is inserting into the same table.

Is there any safe trick to avoid deadlock ?! Im already using DDL_LOCK_TIMEOUT in the DDL session.

To reproduce the problem , I run 2 sessions : Session-1 runs a INSERT loop loading TEST table , commiting every 20 records, session-2 , performs ALTER TABLE... add constraint novalidate and DROP CONSTRAINT in a loop.

Session-2 is able to add and drop the constraints 100s of times, then drop constraint times out a few times (expected behaviour from ddl_lock_timeout)  but then fails with a deadlock sporadically , which I want to eliminate.

Oracle Ver is 11.2.0.3 .

Thanks,
Vasu

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