An outer transaction is a set of operations performed in the Oracle Endeca Server data store that is viewed as a single unit.
If an outer transaction is committed, this means that all of the data and configuration changes made during the transaction have completed successfully and are committed to the data files (index).
If any of the changes made within a transaction fail to complete successfully, the outer transaction fails to commit and remains open (only one outer transaction can be open at a time). In this case, you can roll back the entire transaction, and the changes to the data files (index) do not occur.
In general, the best practice is to set up operations so that successful updates are automatically committed (this is the default), but failed updates can be rolled back either automatically or manually.
The Transaction Web Service of an Endeca data store is used for controlling outer transactions.