A data process apparatus (100 1, 100a) for sharing shared data stored therein among a plurality of data process apparatuses (100 1, 100 4, 100a-100n) participating in an event, the data process apparatus comprising: a participation notification reception unit configured to receive a participation notification indicating participation to the event from each of the plural data process apparatuses including first and second data process apparatuses in the event; a storage unit configured to store first and second lists therein, the first list including transmission completion data indicating one or more of the plural data process apparatuses that has completed transmission of the shared data, the second list including ongoing transmission data indicating one or more of the plural data process apparatuses that is currently transmitting or receiving the shared data; a notifying unit configured to notify the second data process apparatus as a data obtain target from which the shared data is to be obtained, to the first data process apparatus; wherein the second data process apparatus is a data process apparatus from which the participation notification has already been received by the participation notification reception unit; wherein the notifying unit is configured to determine the second data process apparatus as the data obtain target based on a data share status of the second data process apparatus and a data transmission status of the second data process apparatus; by referring to the first and the second lists and identifying from them at least one of the plural data process apparatuses that has already obtained shared data and is not currently transmitting the shared data; and wherein the identified one of the plural data process apparatuses is determined as the data obtain target; wherein in a case where the notifying unit identifies more than one of the plural data process apparatuses, the notifying unit is configured to identify the one of the plural data process apparatuses according to an order in which the participation notification is received by the participation notification reception unit; and wherein the notifying unit is configured to determine the data process apparatus itself as the data obtain target in a case where the one of the plural data process apparatuses cannot be identified from the first and second lists, whereby shared data stored in the data processing apparatus itself is the data to be obtained. a participation notification reception unit configured to receive a participation notification indicating participation to the event from each of the plural data process apparatuses including first and second data process apparatuses in the event; a storage unit configured to store first and second lists therein, the first list including transmission completion data indicating one or more of the plural data process apparatuses that has completed transmission of the shared data, the second list including ongoing transmission data indicating one or more of the plural data process apparatuses that is currently transmitting or receiving the shared data; a notifying unit configured to notify the second data process apparatus as a data obtain target from which the shared data is to be obtained, to the first data process apparatus; wherein the second data process apparatus is a data process apparatus from which the participation notification has already been received by the participation notification reception unit; wherein the notifying unit is configured to determine the second data process apparatus as the data obtain target based on a data share status of the second data process apparatus and a data transmission status of the second data process apparatus; by referring to the first and the second lists and identifying from them at least one of the plural data process apparatuses that has already obtained shared data and is not currently transmitting the shared data; and wherein the identified one of the plural data process apparatuses is determined as the data obtain target; referring to the first and the second lists and identifying from them at least one of the plural data process apparatuses that has already obtained shared data and is not currently transmitting the shared data; and wherein the identified one of the plural data process apparatuses is determined as the data obtain target; wherein in a case where the notifying unit identifies more than one of the plural data process apparatuses, the notifying unit is configured to identify the one of the plural data process apparatuses according to an order in which the participation notification is received by the participation notification reception unit; and wherein the notifying unit is configured to determine the data process apparatus itself as the data obtain target in a case where the one of the plural data process apparatuses cannot be identified from the first and second lists, whereby shared data stored in the data processing apparatus itself is the data to be obtained.