A compare fails with the following error in the compare log "Oracle Error: ORA-01466: unable to read data - table definition has changed
DDL performed on a table while it is being compared is not supported. Please wait until the DDL has posted and restart the compare. The only way to avoid this would be to lock the source table during the length of the compare.
The sysdate of the database on source was not same as system date, the database sysdate was one day ahead of the system date, so the creation time of the table was more than the time on target, wait till the target time reaches the creation time of the table on source and then run compare.