In import mode of Mload, update's and delete's to be sucessful, they must refer Primary Index in the where clause.
Please let me know the exact reason for the above statement ?
what happens if I wont specify PI in where clause in delete/update statement in Mload(import mode) ?
"exact reason" - what do you expect?
multiload was designed to avoid journaling and therefore it came up with some rules - one is that the full PI has to be refered as it need to know which blocks are affected. Only exception is "multiload delete" run type.
Did you read the manuals?
"what happens if I wont specify PI" - you get an error message and nothing will be processed.