SSMA tool includes Extension Pack which installs sysdb database on the target SQL server environment to emulate Oracle/Sybase functionalities. There is a known issue for installing SSMA extension pack  when the target SQL Server is a clustered enviroment. We are planning to address this issue in the future release. As a workaround, we published a KB article on manually install Extension Pack on a SQL Cluster. You can find the KB article here.