ATPREF is a standard SAP Structure so does not store data like a database table does. It can be used to define the fields of other actual tables or to process "ATP: Data for Reference between Documents" 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_ATPREF TYPE ATPREF.
The ATPREF table consists of various fields, each holding specific information or linking keys about ATP: Data for Reference between Documents data available in SAP. These include DELNR1 (MRP element number), DEL12_1 (MRP element number), DELKZ1 (MRP element), ATPIF1 (ATP Server: Additional information field for 'shared buffer')... See below for full list along with technical details, documentation, text table, check tables, foreign key relationships, conversion routines, relevant tcodes and example ABAP select code etc. .