In general to find out more, run transaction ST05 (Performance Trace) before the process (e.g. real posting in RERAPP) and read the (insert) statements.
How to switch between tables for posted doc. if You select type of contract before:
Table: VICNCN
Point out: BUKRS (Company Code) and RECNTYPE(Contract Type)
Output Key: INTRENO (RE Key).
Then move to the cash flow tables.
Tables: VICDCFPAY (Payment-Related Cash Flow), VICDCFOBJ (Object-Related Cash Flow);
Point out: INTRENO (RE Key), CFSTATUS EQ 'I'
Output Key: REFGUID (Document References in Cash Flow) used by VIRADOC-DOCGUID
Then move to the document tables.
Table: VIRADOC
Point out: DOCGUID (GUID: RE Doc.)
Output Key: (DOCGUID, PROCESSGUID - used by VIRADOCITEM), REFDOCID used by BKPF-AWKEY, PROCESSID used by BKPF-XBLNR
Table: BKPF
Point out: AWKEY (Reference Key), BUKRS (Company Code), GJAHR (Fiscal Year), XBLNR (Reference)
Output Key: (BUKRS, BELNR, GJAHR - used by BSEG), (AWKEY, GJAHR) used by COBK
Table: COBK
Point out: REFBN (first 10 char of AWKEY) and AWORG (last 10 char of AWKEY), KOKRS (CO Area), GJAHR (Fiscal Year)
Output Key: (KOKRS, BELNR - used by COEP);
If You review the data there is a space to increase performance by filtering (contracts validity, reference transaction AWTYP etc.). I omitted reversed doc.