SQL queries to clean most of the log and extra data that is not mandatory. Don't use it if you need to debug problems or if you are exporting/importing data. TRUNCATE dataflow_batch_export; TRUNCATE dataflow_batch_import; TRUNCATE log_customer; TRUNCATE log_quote; TRUNCATE log_summary; TRUNCATE log_summary_type; TRUNCATE log_url; TRUNCATE log_url_info; TRUNCATE log_visitor; TRUNCATE log_visitor_info; TRUNCATE log_visitor_online; TRUNCATE report_viewed_product_index; TRUNCATE report_compared_product_index; TRUNCATE report_event; TRUNCATE index_event; TRUNCATE catalog_compare_item; Note: Not all the tables are available on versions before version 1.8 You can freely delete in the web root folder logs - var/log/* cache - var/cache/* reports - var/report/* exports (your exported data!!!) - var/export/* session (also your current sessions - if they are saved in those files) - var/ssession/* temp files (usualy the folder is empty) - var/tmp/*...