Retreive Error Message from sap BDC

While doing call transaction, if an error occurs in updation, we declare bdcmsgcoll and store our messages in it, but how to retreive error message from it

Using function module 'FORMAT_MESSAGE' you can capture the messages.

Here is a sample of the program code for that:

LOOP AT it_messtab.
CALL FUNCTION 'FORMAT_MESSAGE'
EXPORTING
id = it_messtab-msgid
lang = it_messtab-msgspra
no = it_messtab-msgnr
v1 = it_messtab-msgv1
v2 = it_messtab-msgv2
IMPORTING
msg = g_msg
EXCEPTIONS
OTHERS = 0.
IF it_messtab-msgtyp = 'S'.
it_sucess-sucess_rec = g_msg.
it_sucess-lifnr = it_header-lifnr." Based on your field
it_sucess-tabix = v_lines.
APPEND it_sucess.
ELSEIF it_messtab-msgtyp = 'E'.
it_error-error_rec = g_msg.
it_error-lifnr = it_header-lifnr.
it_error-tabix = v_lines.
APPEND it_error.
ELSE.
it_info-info_rec = g_msg.
it_info-lifnr = it_header-lifnr.
it_info-tabix = v_lines.
APPEND it_info.
ENDIF.
ENDLOOP.