Ok this was already answer Here…..
1. This feature was designed to let you change the table prefix to something other than jos_ which was used in Joomla! 1.5 and 1.6. Joomla! 1.7 and later use, by default, a random database table name prefix when installing. This made this feature obsolete. If you are using a third party installer which uses jos_ it is a major security bug in the third party installer and the proper long term course of action is getting in touch with its developers and ask them to fix it.
2. The proper way to change the database prefix without risking bricking your site is:
- Take a backup with Akeeba Backup
- Restore the backup. In the Database Restoration page choose a different prefix.
- Delete the tables with the jos_ prefix from your site using phpMyAdmin, Adminer or any similar tool provided by your host
The “ way to change the database prefix” given here is a good tip but not really a practical way as restoring a complete web site even using Akeeba can become rapidly a complex method.
Remember that using PHPMyAdmin
you can easily change de prefix by selecting the table
s and use the “Replace Table Prefix” command
On Mamp PHPMyAdmin, you have to enter the old prefix … Say —> a3fyo (I enter without the underscore) to the new one... Say —> v5s5f
Remember to change the configuration.php to reflect your change
public $dbprefix = 'v5s5f_';
You can close that ticket