Increase upload file size limit of TestLink

Edit /etc/php.ini file

upload_max_filesize = 100M
max_execution_time = 600

Edit
/var/html/www/testlink/config.inc.php
$tlCfg->import_file_max_size_bytes (config.inc.php): 8192000
$tlCfg->import_max_row (config.inc.php): 100000
$tlCfg->repository_max_filesize (config.inc.php): 8 // MB

restart Apache
service apache2 restart
or
service httpd restart