A non FATAL error is an error that does not force the session to stop on its first occurrence. T check the occurence we can set the stop on error option in the session properties and the integration service counts these errors.
There are mainly three typr of non fatal errors:
This error happens while reading from the database source or flat files or any other kind of source systems.
This error occurs while writing to a Target or Database.
This error is encountered by Integration service while transforming the data.
The fatal error results in stopping the session. All the reading and writing are stopped and it roll back all the data that is not commited to the target database.
This happens when their is a loss of connectionand not able to access the source ,target or repository. This can include loss of connection or target database error, such as lack of database space to load.