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Introduction
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Commands & Actions
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Transaction Sequence
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MasterPass
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Visa Checkout
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Foreign Exchange
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Parameter Description & Action
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Gateway Domain Knowledge
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Transaction Result Codes
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Out Of Band
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Payment Facilitator
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Tokenization
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SOAP API
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Pos Device Intergration
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Acquire Contact Information
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3D Secure
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Enterprise API Samples
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Card on File
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Additional Data Transactions
Duplicate transactions
A problem of a duplicate transaction can occur if a merchant submits a previously successful transaction in a new request. A duplicate transaction of this nature is typically due to a user's unintentional mistake, e.g. pressing the “Submit” button twice, or submitting the same batch twice. It is responsibility of the merchant to ensure that a single transaction request is not submitted successfully more than once.
Nevertheless, the iVeri Gateway provides three mechanisms to protect against duplicate transactions. Specifying a unique MerchantTrace is a client-side configuration, while the latter to require contacting your local distributor.
Specify a unique Merchant Trace for each step in a Transaction Sequence
A MerchantTrace is a unique identifier for each request sent to the gateway and is an optional parameter. The MerchantTrace corresponds to a database index that was generated by the merchant before a request was sent to the gateway. In short, the MerchantTrace refers to a particular step in the transaction sequence.
The recommended way to control duplicate transactions is to always specify a MerchantTrace. This has two benefits.
If a merchant does not receive a reply to a request, then they have the choice of either voiding or retrying the transaction by using the same MerchantTrace.
A merchant can re-use a MerchantReference with different MerchantTraces for the same TransactionIndex.
Merchant Reference validity period
- A MerchantReference is a unique identifier allocated by the merchant for a transaction sequence.
- The MerchantReference validity period is a mechanism to protect merchants against undesired double debiting.
- When performing an initial transaction request (i.e. no TransactionIndex provided), then if the last use of that MerchantReference (within a time period) was a successful, then a new Transaction is not performed.
- When performing a follow up transaction (i.e. TransactionIndex provided), then if the last use of the MerchantReference (within a time period) of the same transaction type was successful, then a new Transaction is not performed. [Assuming the Transaction Type Repetition option has not been activated].
- The default time period (Merchant Reference validity period) discussed above is 6 months. This can be changed to a minimum of 3 days.
Recurring transaction checking
- The Recurring transaction checking period is an additional mechanism to protect merchants against undesired double debiting.
- By default, recurring transaction checking is disabled.
- When enabled, if a transaction is attempted with the same PAN, Amount, Command combination, but a different MerchantReference as a previously successful transaction done within a period, then the subsequent transaction request will fail.
- If a Merchant explicitly requests this to be enabled, a time period (in seconds / minutes / hours) should be specified. This is typically 5 minutes.
- If a Merchant uses MerchantTrace to uniquely assign each individual transaction before submission to the iVeri Gateway, then this option should not be needed.
- This option is recommended for merchants who are forced to have poor state handling - for example those that generate a merchant’s reference in memory and only write to the database after sending a request to the iVeri Gateway.
- Note that even when this option is disabled, an acquirer or issuer “downstream” may have their equivalent option enabled
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