Changing permalink might be a big issue for every blogger because their might be a big change of loosing all traffic. If you change your permalink without using any plugin then your all permalink will be changed into the new one therefore you will be 404 error when your user want to see the post that is being already indexed in search engine. Therefore to eradicate this problem you have to use the plugin which helps to redirect all you previous post to the new permalink structure which is called 301 redirection method. It is most beneficial for the user who migrate from blogger to self hosted wordpress blog or migrate from wordpress.com to self hosted wordpress blog. Before changing you must have knowledge which permalink structure is best for you
Thanks to Dean lee Permalinks migration plugin which make it possible to change permalink without loosing any traffic. The plugin will generate a ” 301 redirection” or you can call it permanent redirection when bots will crawl your posts.