At what point in the migration do you get the error and are you making an online or offline migration ?
Can you detail the steps youhave made until you get the error ?
If you are making an online migration then when you get to the 'Target Database' step change the mode to 'Offline' to generate the scripts and click finish.
If you get the erro during the 'Move Data' step then change the mode to offline and continue from there.
THis gives more control over what is happening and should enable you to see what is causing the problem.
I perform an offline migration. I get this error after i initiate an offline migration choosing online source and offline for target ie I pointed a filder for the script generation. As the migration faied no scripts and log files was generated in the folder.
Can you try the migration again with the latest version of SQLDeveloper (220.127.116.11)?. It will generate a log file in the project directory. So we will have an idea as to where the failure occurs. Secondly you can also try the migration in phases i.e.
1. Just perform a capture first. To do so, on the capture phase screen (online/offline source selection), click on the 'Go to Summary Page' option at the bottom of the screen.
2. Complete the capture process.
Repeat the same steps again for just convert and then generate also.