When doing an enrollment into the vault for a Mastercard card, you will possibly receive a transactionLinkIdentifier in the response.
This is a unique identifier for the transaction and is required for subsequent transactions using the vault access token.
You should store this identifier in your system and pass it in the sequenceInfo object when initiating a subsequent transaction using the vault access token.
Not all Mastercard transactions will return a transactionLinkIdentifier. If you do not receive one, you do not need to pass it in the subsequent transaction.
It depends on your account setup and the acquirer used for the transaction. Please contact CCV support if you have questions about this.