Unfortunately it is not possible to import all MLS listings into a database; in most cases this is not legal, and the current version of the IDX Broker API does not support this function. To display All MLS Listings please use "Live MLS feed" integration. You can find more information about it in the table here.
If you integrate Live MLS Feed (via Dynamic Wrappers) - these listings are stored on the IDX Brokers server and because of it you cannot access / modify it. It is possible only to display as a part of your IDX Broker Pages.