There are two ways of manipulating Magento catalog, customer and sales information.

1. Using the Magento admin panel, third party extensions to the Magento instance or direct programming against the Magento core objects
2. Direct database edits to the Magento instance database, use of Magento import/export functionality

The first category passes all data manipulation through the Magento core object model. This allows extensions such as Codisto to capture those edits and signal the changes to be sent to other marketplaces.

The second category of changes are notoriously difficult to track. Traditionally, the only way to detect such changes is to fully scan the entire database, which in general will use too much server resources and affect the performance of the Magento website.  

Codisto has solved tracking both types of changes optimally without the need for custom programming or engineering.  However, if Codisto is uninstalled for any reason, it may be necessary to install the codisto.php shell helper into the Magento instance. This script and usage instructions are available at Codisto-Shell.