Usually Enterprise Bridge does not store data on migration server. It does not include and does not require any internal or external database system. It is just a pipe for data transfer and transformation between source and target system.
The data flow directly from source to target system through secure data pipeline. Occasional fragments and caches might remain in temporal folders of migration server as a result of transformation in a temporary folder of the OS where Enterprise Bridge runs. It is recommended to cleanup this data periodically for additional security.
Logs of processing are stored as text files in application data folder on local disk. Configurations are stored in application data folder as JSON files.