Woocommerce hook before checkout page submit and after order created

functions.php

<?php
//triggers before checkout form is submited but order will be created.
add_action( 'woocommerce_checkout_update_order_meta', 'cpm_woocommerce_checkout_update', 10, 2 );
function cpm_woocommerce_checkout_update($order_id, $data) {
/*write ur code*/
}

Thank you.