Show an urgent message in the WordPress admin area

wp-showAdminMessages.php

<?php

function showMessage($message, $errormsg = false){
    if ($errormsg) {
        echo '<div id="message" class="error">';
    } else {
        echo '<div id="message" class="updated fade">';
    }

    echo "<p><strong>$message</strong></p></div>";
}  

function showAdminMessages() {
    showMessage("You need to upgrade your database as soon as possible...", true);

    if (user_can('manage_options') {
       showMessage("Hello admins!");
    }
}

add_action('admin_notices', 'showAdminMessages');