Im using the currency conversion FM as below
CALL FUNCTION 'CONVERT_TO_LOCAL_CURRENCY'
DATE = SOURCE_FIELDS-/BIC/SST_UP_DT
FOREIGN_AMOUNT = SOURCE_FIELDS-/BIC/SSUBTOTA3
FOREIGN_CURRENCY = SOURCE_FIELDS-DOC_CURRCY
LOCAL_CURRENCY = SOURCE_FIELDS-LOC_CURRCY
RATE = EX_RATE
TYPE_OF_RATE = 'M'
READ_TCURR = ' '
LOCAL_AMOUNT = VALUE
what is the significance of the parameter READ_TCURR?
if you look at the definition of the import parameters of this function it describes that "READ_TCURR" means "Read exchange rate from table TCURR".
Basically you have two options when using this FM: either you pass an exchange range in the parameter RATE or you tell the FM to get a valid exchange rate (based on the other parameters you are passing to this FM) by passing an X in the parameter READ_TCURR.