When trying to use Schema compare for Oracle, the following message appeared and comparison failed with no detailed information...
"The given key was not present in the dictionary"
There is not much detail on the issue , but to work around this, carefully watch the progress as the comparison is running..
Then look at the options for your project, there may be a switch to ignore the item it was last doing before it fell over.
Try this or a similar /related option, or just try a few to see if it works and narrow it down.
I found on this occasion, the 'Ignore permission' option allowed me to continue, but i would love to know which object was causing this error.
You may have similar issues on other comparison groups. Hopefully this technique will help provide a workaround if a cure is not possible.
For further information, you may want to try enabling verbose logging see this link on instructions....