Unlike settype, relationship does not have a dedicated read function module maintained in its metadata table. Instead, the generic read function module COM_IL_DB_READ is used.
Below is a simple explanation about each parameter of FM COM_IL_DB_READ, using read on relationship PRDCPN for example.
IV_RELTYPE
PRDCPN - relationship name
IV_ATTR_TYPE
COMT_IL_PRDCPN_ATTR_TYPE - contains relationship specific business data, in this example, the customer product id is stored in field PRID_VENDOR
