Hi Layale, [...]

On another hand, I read in the wiki that I need to truncate the following tables: * bibio * biblioitems * items * auth_header * sessions * zebraqueue

As a help to truncate these table, you may use phpMyAdmin. And this may be of help too: http://stackoverflow.com/questions/8641703/how-do-i-truncate-tables-properly\ Arslan