Currently there is only one option under the General section, but it takes some explanation.
Consider any dates past the "Release Days" as only available for Online Reservations -- Set this option if you want to consider sites as unavailable for local reservations if it's available for online reservations, according to the Release Days field(s) for each site.
As mentioned in Data Fields Used, there is a "Release Days" field for each of the types of online reservation services that can be uploaded to (Webervations and the Export to Web for your own web site), and also for the Reservation Friend service since they support this functionality. If one or more of these fields is enabled, and also assuming that the site is not excluded from that type of online reservations, then the site will be marked as unavailable for local reservations after the # of release days specified.
As an example: If you have the Release Days for Export to Web set to 3, then that means the site is released from online availability 3 days ahead of time (3 days from today). That also means that it's available for online requests starting 3 days from now (e.g. someone could be reserving the site online for any dates 3 days from now or later). Therefore, you should avoid making local reservations for it that might conflict with the online reservations. Setting this option will make the site show as unavailable on the Rack starting 3 days from now (e.g. the first 3 days will be available, but after that it will be considered unavailable for locally made reservations).
Sites that are considered available for online reservations in this manner are shown in a different color on the Rack (a medium blue by default, different than the normal grey for unavailable). They will also be excluded from the list of available sites any time "Show Available" or "Available Only" is selected.
Note that if an attempt is made to create a reservation covering an online-only date, either a warning or error will be shown depending on the Access Levels setting and the current operator's level. If the operator doesn't have access to make local reservations for online-only dates, an error will be shown and the reservation cannot be saved. The access level required is Manager by default, but it can be modified through Maintenance / Park Setup / Access Levels.