The database consists of an Acquisition table, which lists which radio frequencies to search for in which areas, and a System table, which tells the phone which towers it is allowed to connect to, and the preferred order. All other zones will be updated as well. Not all hacking is good, kids, and when it adversely affects the network, it makes the other, good kind of hacking look bad. Previously on Android A to Z: If you're in an area with weak but steady signal from your carrier, the PRL will connect you to that signal rather than connect to a stronger signal on a different carrier. Without a correct and valid PRL, your phone won't be able to roam outside your home network, and may not be able to connect at all inside the network.