Why are some messages in the archive but not others?

The archive is the permanent long-term home for On Call Central call records. Archived calls are available in the in the "Archive" subtab of the web interface Dashboard, but no longer are accessible through the On Call Central telephone interface. This helps prevent situations in which providers call in and hear, "You have one new message, and 547 old messages." Nobody likes that, hence the concept of the archive.

Calls land in the archive via one of three mechanisms. These mechanisms are listed below in decreasing order of frequency:

1. They are sent to the archive by the auto-archiver. The auto-archiver systematically sends outdated calls to the archive. You can set the interval at which the auto-archiver will move calls to the archive in Settings->Account Properties.
2. The provider sent the call to the archive manually via either the mobile application or the On Call Central telephone interface. 
3. Someone selected the call in the Dashboard on the web interface and manually sent it to the archive. 

If you are looking for a recent call, but do not see it on the dashboard, take a look in the archive. Chances are it was sent there manually via mechanism #2 or #3.