The time at which streams were committed in microseconds
granularity. This field will only exist when there are no
stream errors. **Note** if this field is not set, it means
the commit was not successful.
Stream level error if commit failed. Only
streams with error will be in the list.
If empty, there is no error and all streams are
committed successfully. If non empty, certain
streams have errors and ZERO stream is committed
due to atomicity guarantee.