What happens when you read large blob data from Oracle db using jdbc connection?

[mahavir swami]

when we try to read blob data from an oracle db using jdbc connection
like

Connection con = DriverManager.getConnection(connectionurl, username, password);
PreparedStatement ps = con.prepareStaement("select blob_data from table_name");
ResultSet rs = ps.executeQuery();
Blob blob = rs.getBlob(1);

now suppose the blob data is having size more than 80MB , i mean its large data, then how does
jdbc code in oracle driver class interacts with data base to read such large data from db?