Transactions introduce dynamism into a cryptocurrency system. They are the only way of altering the state of an account. A newly created transaction that has not yet been included in a block is called an unconfirmed transaction.
Unconfirmed transactions are not guaranteed to be included in any block. As a result, unconfirmed transactions have no effect on the account state. The account state is only updated when a transaction is included in a harvested block and thereby confirmed.
Different types of transactions exist. Each type has a specific purpose, e.g. transfer XEM from one account to another or convert an account to a multisig account. Since transactions consume resources of the p2p network there is a fee for each transaction. The fee depends on the transaction type and other parameters of the transaction. Transactions have a deadline. If a transaction is not included in a block before its deadline, the transaction is considered expired and gets dropped by the network nodes. The following sections describe the different transaction types.
A transfer transaction is used to transfer XEM from one account to another. A small message of at most 96 bytes can be attached to each transfer transaction. In the case of an encrypted message, only 48 bytes can contain custom data because the salt and the IV data are part of the encrypted message and require 48 bytes.
NEM allows an account to lease its harvesting power to another account through an importance transfer transaction. This is known as delegated harvesting. This allows the original account to use its importance to harvest on a remote server (such as a virtual private server (VPS)) without needing to have its private key openly exposed on the server. In fact, this feature allows accounts in cold storage to harvest without putting any funds at risk.
The fee for an importance transfer transaction is 6 XEM