Hello. This is Klaytn API Service team.
Please refer to the following information about switching to GFP.
Before getting into the details on how to switch to GFP, let's first discuss what GFP is and how it is different from UFP. First, GFP (Global Fee Payer) is a service that allows BApp's operators to pay fees in arrears, instead of making customers pay for the transaction costs incurred in operating the service. Because Ground X constantly monitors the balances, it reduces the burden on customers to constantly purchase or recharge KLAY. Conversely, when using UFP (User Fee Payer), the customer will create a separate pool that pays and manages the fees themselves. For more information about GFP, please refer to the posts regarding charging mechanism of GFP and general information on GFP.
For customers who are using the UFP through a contract created through Caver, the GFP cannot be set up directly using KAS. In this case, you can enable GFP by issuing RLP encoded transactions. First of all, please change to SenderSigned→transaction.getRLP by referring to the example below and the document so that KAS, not sender, pays the fee.
Example : > transaction.getRLPEncoding()
Please refer to Klaytn Design - Transaction for specific instructions on creating an RLP encoding string for each transaction type.
Next, change the fee ratio setting to '0'. Fee ratio refers to the ratio (1%-99%) to be paid by the feePayer out of the total transaction fee. In the case of GFP, KAS fee payer account pays for the transaction fee, therefore it should be set to '0' so that the user does not bear the cost.
Klaytn API Service team.