How do I clean up the sessions table?
Go to your Drupal installation directory     /sites/default/settings.php and add the following line

ini_set('arg_separator.output',     '&amp;amp;');
ini_set('magic_quotes_runtime',     0);
ini_set('magic_quotes_sybase',      0);
ini_set('session.cache_expire',     10800);
ini_set('session.cache_limiter',    'none');
ini_set('session.cookie_lifetime',  10800);
ini_set('session.gc_maxlifetime',   10800);
ini_set('session.save_handler',     'user');
ini_set('session.use_only_cookies', 1);
ini_set('session.use_trans_sid',    0);
ini_set('url_rewriter.tags',        '');
ini_set('session.gc_probability', 1);