SAP has a special cluster tables located in SAPSR3.RFBLG table (as of Oracle RDBMS), which contains compressed blob data for tables like BSEG, BSET, BSEC, BSED, etc.
There is a speculation that at some distant point of history, Oracle RDBMS didn't have support for >256 columns, but SAP needed more (>300), so they packed all columns into compressed blob.
I've just written an utility to unpack these tables, here are first ~60 columns (empty columns are suppressed) for demo IDES database:
unpack_chunk() name=BSEG MANDT=800 BUKRS=0001 BELNR=0100000000 GJAHR=1995 BUZEI=001 BUZEI:  BSCHL:  DMBTR: [6,14] WRBTR: [12,00] PSWBT: [6,14] PSWSL: [EUR ] VALUT:  ZUONR: [19950606 ] SGTXT: [(text) ] VORGN: [RFBU] HKONT:  unpack_chunk() name=BSEG MANDT=800 BUKRS=0001 BELNR=0100000000 GJAHR=1995 BUZEI=002 BUZEI:  BSCHL:  DMBTR: [6,14] WRBTR: [12,00] PSWBT: [6,14] PSWSL: [EUR ] ZUONR: [19950606 ] VORGN: [RFBU] KOKRS:  HKONT:  unpack_chunk() name=BSEG MANDT=800 BUKRS=0005 BELNR=0100000000 GJAHR=2005 BUZEI=001 BUZEI:  BSCHL:  DMBTR: [60000,00] WRBTR: [60000,00] PSWBT: [60000,00] PSWSL: [EUR ] VALUT:  ZUONR: [20051231 ] SGTXT: [Test for Allocation FI ] ALTKT:  VORGN: [RFBU] FDLEV: [F0] FDWBT: [60000,00] FDTAG:  KOKRS:  HKONT: 
It's somewhat unfinished, but the source code is available: https://yurichev.com/tmp/SAP_cluster_unpacker.tar.bz2.
→ [list of blog posts, my twitter/facebook]Please drop me email about any bug(s) and suggestion(s): dennis(@)yurichev.com.