SALV_S_APPEND_REF is an SAP Structure so does not store data like a database table does but can be used to process "Append Lists" Information within sap ABAP programs. This is done by declaring abap internal tables, work areas or database tables based on this Structure. These can then be used to store and process the required data appropriately.
i.e. DATA: wa_SALV_S_APPEND_REF TYPE SALV_S_APPEND_REF .
Below is the documentation avaialable and full details of the fields which make up this Structure.
|Data Type||length (Decimals)||Check table||Description||Conversion Routine|