DMS Requirement to Disable Foreign Keys

Question

A number of DMS documents seem to indicate that it is a _requirement_ to disable foreign key constraints when performing a full load \[1,2,3,4]. However, in my initial tests, I've found that this doesn't _seem_ to be necessary, despite the fact that I am migrating data with foreign key relationships.  
  
Specifically, I'm migrating an on-premise Oracle database to an RDS Oracle database, using the _full-load-and-cdc_ option. My complete schema has already been created on the target as a prerequisite to the migration (therefore, I'm using the _DO_NOTHING_ table preparation mode), including all foreign key constraints. I have successfully migrated the data from all 16 tables, which have related data constrained by foreign keys, _without_ having to disable the foreign key constraints (nor make any other changes to my target schema).  
  
Can someone elaborate on the conditions in which foreign keys must/should be disabled for migration?  
  
\[1] https://d0.awsstatic.com/whitepapers/RDS/AWS_Database_Migration_Service_Best_Practices.pdf  
\[2] http://docs.aws.amazon.com/dms/latest/sbs/CHAP_On-PremOracle2Aurora.Steps.CreateTask.html  
\[3] http://docs.aws.amazon.com/dms/latest/userguide/CHAP_Introduction.html  
\[4] https://d0.awsstatic.com/whitepapers/strategies-for-migrating-oracle-database-to-aws.pdf

Answer

I've confirmed that foreign keys are not always required to be disabled; they only need to be disabled under certain conditions. For example, per the above when using the direct path load \[1] along with the "do nothing" table preparation mode \[2], foreign keys need not be disabled. However, when using the conventional load or other table preparation modes, they must be disabled. There may be other conditions to consider as well.  
  
\[1] http://docs.aws.amazon.com/dms/latest/userguide/CHAP_Introduction.ConnectionAttributes.html#CHAP_Introduction.ConnectionAttributes.Oracle  
  
\[2] http://docs.aws.amazon.com/dms/latest/userguide/CHAP_Tasks.CustomizingTasks.TaskSettings.FullLoad.html

DMS Requirement to Disable Foreign Keys

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