多进程方式访问eXtremeDB

    eXtremeDB作为一种内存数据库，可以根据实际应用的需要，使用多样的内存，比如本地内存，共享内存，NVRAM等等。在实际的应用中，有时候会存在运行在同一台server上的多个应用访问部署在同一个server上的eXtremeDB，这时候就需要使用共享内存来存储数据供多个应用访问。
    当使用共享内存时，eXtremeDB可以由其中的某一个应用来初始化创建，或者由单独的一个进程来创建。而其它的应用只需要直接连接eXtremeDB。部分代码示例如下：

/* start eXtremeDB runtime */
  /* optionally set access mode, default is 0666 */
  mco_runtime_setoption(MCO_RT_OPTION_UNIX_SHM_MASK, 0600 );
  rc = mco_runtime_start();
  if ( rc == MCO_S_OK ) {

    /* try to connect to database first */
    rc = mco_db_connect( db_name, &connection );

    if ( MCO_E_NOINSTANCE == rc ) {

      /* No db found. Open the database and perform tasks of the main process */
      rc = open_database( db_name, simpledb_get_dictionary(), DATABASE_SIZE, CACHE_SIZE,
                                   MEMORY_PAGE_SIZE, PSTORAGE_PAGE_SIZE, 1, &dbmem );

      if ( MCO_S_OK == rc ) {

        /* connect by name */
        rc = mco_db_connect( db_name, &connection );

        /* disconnect */
        rc = mco_db_disconnect( connection );
      }

    } else if ( MCO_S_OK == rc ) {

      /* database connection successful, perform tasks of the secondary process */
      printf("\n\n\tConnection successful, perform tasks from secondary process...\n" );

      /* don't forget to disconnect when done */
      rc = mco_db_disconnect( connection );
      sample_rc_check("\tDisconnect secondary process", rc );

    } else {
      /* handle unexpected error on connect */
    }

    /* stop eXtremeDB runtime */
    mco_runtime_stop();
  }