1. Ensure that initialization parameters are set as O7_DICTIONARY_ACCESSIBILITY=TRUE
REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE or SHARED
2. Make sure that the temp tablespace size is bigger than the largest object size to be migrated. In one of our iterations, the size of the biggest object to be migrated was an index called WF_ITEM_ATTRIBUTE_VALUES_PK of size 9GB. We made sure that our temp tablespace had more than 9 GB of free space before starting the migration.