Hi SriLalitha,
Are you sure that the field RELDT exists in the APO Structure /SAPAPO/CIF_MATLOC?? I dont find it in my system. Is it /SAPAPO/MATLOC or /SAPAPO/CIF_MATLOC?? check once again.
Anyways if you find,then no need of calling BAPI in APO exit, try to populate the field RELDT of /SAPAPO/CIF_MATLOC from /SAPAPO/CIF_MATLOCCUS.
I attached the note,which i mentioned earlier. This will be handy for you.
Thanks,
Santosh KB.