insert data in to inheritance table gives error

Hi 

I am facing error inserting data in a table of retail _RetailPeriodicDiscount in dynamics AX 2012 R3 by x++ code table has inherited property how can i insert data in inherited table my code is below

and my Facing the following error.

Database insert operation is not allowed on an abstract table.

static void CreateDiscountScheem_3(Args _args)
{
RetailPeriodicDiscount _RetailPeriodicDiscount;
NumberSeqFormHandler numberSeqOfferId;
LedgerDimensionDefaultAccountController discountDimAccController;
///----- Field-------
RetailOfferIdEx3 OfferId;
Name DiscountScheemName;
//RetailDisabledEnabled ScheeemStatus;
int ScheeemStatus;

CurrencyCode Currency;
RetailDiscountConcurrency _ConcurrencyMode;
Status _ActiveInActive;
RetailDiscountPercentValue _DiscountPercentValue;
ValidFromDate _ValidFrom;
ValidToDate _ValidTo;
RefRecId _PriceDiscGroup;
RetailMemo _Description;
RetailDiscountOfferTypeBase _PeriodicDiscountType;

NumberSeq num;
str test;
//////////////////////////
ScheeemStatus=1;
_DiscountPercentValue=20;

// NumberSeq NumberSeq;
ttsBegin;
num = NumberSeq::newGetNum(RetailParameters::numRefOfferId());
test=num.num();
_RetailPeriodicDiscount.OfferId =test;
_RetailPeriodicDiscount.Name=DiscountScheemName;
_RetailPeriodicDiscount.Status=1;//ScheeemStatus;
_RetailPeriodicDiscount.CurrencyCode='PKR';
_RetailPeriodicDiscount.ConcurrencyMode= (RetailDiscountConcurrency::Exclusive);
_RetailPeriodicDiscount.DiscountPercentValue=_DiscountPercentValue;
_RetailPeriodicDiscount.DiscountLedgerDimension=5637144584;
_RetailPeriodicDiscount.ValidFrom =23\07\2019;
_RetailPeriodicDiscount.ValidTo=31\07\2019;
_RetailPeriodicDiscount.DateValidationType =RetailDateValidationTypeBase::Standard;
_RetailPeriodicDiscount.PeriodicDiscountType=RetailDiscountOfferTypeBase::DiscountOffer;
_RetailPeriodicDiscount.insert();

// info(test);
// num = NumberSeq::newGetNumFromCode(numberSequenceTable::findByNaturalKey('Reta_16').NumberSequence);
// NumberSeq =NumberSeq::newGetNumFromCode(NumberSequenceTable::findByNaturalKey('Reta_16').NumberSequence);
//NumberSeq::newGetNum(RetailParameters::numRefOfferId());

//Info(NumberSeq::newGetNum(FCMParameters::numRefWorkOrderNum()).num());
// _RetailPeriodicDiscount.
ttsCommit;

}