Note: This will have a performance impact on your site, so make sure to turn this off in your production site.
The OSC_DEBUG_DB constant, added in version 2.3, saves the database queries to an array and at the end of the execution the queries are displayed at the end the page. The information saves each query: the sql string, how long that query took to execute, the sql number error and string if there has been some sql error.
The OSC_DEBUG_DB_LOG constant, added in version 2.3, logs the sql queries to a file called queries.log in oc-content. If you want to debug the sql queries of the AJAX calls or cron, you must use OSC_DEBUG_DB_LOG because we can't print these at the end of the page. If Apache doesn't have write permissions, you may need to create the file first and set the appropriate permissions (i.e. use 666).
The OSC_DEBUG_DB_EXPLAIN constant, added in version 2.3, run an EXPLAIN query for each select query and logs the result to a file called explain_queries.log queries. It should be used only during the development of OSClass, themes or plugins to see the performance of the queries. Remember, if Apache doesn't have write permissions, you may need to create the file first and set the appropriate permissions (i.e. use 666).