FMBLEXTCS 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 "Source for Commitments/Actuals in Derivation Tool for BL Ext" 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_FMBLEXTCS TYPE FMBLEXTCS.
The FMBLEXTCS table consists of various fields, each holding specific information or linking keys about Source for Commitments/Actuals in Derivation Tool for BL Ext data available in SAP. These include FISC_YEAR (Fiscal Year), CASH_YEAR (Year of Cash Effectivity), CATEGORY (Budget Category in Funds Management), TRANSAC (CO Business Transaction)... 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. .