When you perform actions that modify operational and transactional data within preview, for example, placing an order or redeeming a coupon, this data is stored in the database, just as they would outside of preview. Your inventory levels and coupon redemption limits can decrease, causing confusion. Also, if you perform analytics on your data, the data created through preview can skew your reports.
To avoid this confusion, you can exclude commands and views from running inside preview by adding them to a preview exclusion file. For example, you can choose to exclude the OrderItemAdd command, disabling items from being added to orders. When a request is made to the Preview web application a check is made by the Preview Adapter to ensure that the name of the command or view that is being requested is not restricted by the preview web application. The Preview Adapter performs this check by ensuring that the command or view does not exist in the preview exclusion file.
By default, no commands are listed in the preview exclusion file.