Field Only and Inversion

Hello SDNers,
I would like to ask you in the datasource there are 2 option si would liek to know when are they used.
1) Inversion
2) Field Only
And Field only does this need to be checked when its custom enhancement t structure or can be checked for other reasons aswell.Please explain.


usually inversion feature is useful for DS carrying customized Keyfigures which has -ve sign
before loading to BW ,the value will be mulitplied by -1 and goes to BW
check this SAP note:
Reverse postings are possible for customer-defined key figures. For this reason, inversion is only possible for certain transaction data DataSources. These include DataSources that have a field that is indicated as an inversion field, for example, the field update mode in the DataSource 0FI_AP_3. If this field has a value, then the data records are interpreted as reverse records in BW.
Set the Inversion indicator if you want to carry out a reverse posting for a customer-defined field (key figure). The value of the key figure is then transferred in inverted form (multiplied by –1) into BW.
filed only..
it is useful when you are enhancing the DS with the userdefined fields and has wriiten the code in CMOD
Sap note:
Field only known in exit
You can enhance data by extending the extract structure for a DataSource using fields in append structures.
The indicator Field only known in Exit is set for fields of an append structure. In other words, by default these fields are not passed onto the extractor from the field list and selection table.
Deselect the indicator Field Only Known in Exit to enable the Service API to pass on the append structure field to the extractor together with the fields of the delivered extract structures in the field list as well as in the selection table.