Hell, yesterday a HLR in Germans O2 network dropped out because an outage (and also the USV dropped out because the outage was too long) and in these moments you see how addicted the world is to mobile communication.
The HLR (Home Location Register) is the place where carriers handles your contract (said simplified) and if a HLR drops, the network isn't able to handle your SIM card correct which means you get "network denied" because your are unknown for the network.
I was on the way to the local tax office and wanted to discuss some stuff with my girlfriend while I was driving (I'm not that good in this tax stuff but my girlfriend is) and can you imagine how I felt not being able to speak with her? Damn... :-(
I had both devices with me - the Smartphone and the Pocket PC with two different SIM cards, unfortunately both SIMs used to be handled in the same HLR so there was no way to make voice calls, setup data connections or even send an SMS (which wouldn't help anyway because also the SIM of my girlfriend is... yes - handled by the same HLR... ;-)).
Well, I haven't searched for a telephone box for the past 5 years or so and finally I've realized there aren't that much telephone boxes in Munich anymore! 8O Seems to be a result of today's cell phone penetration... ;-)
However, after 5 ours of being disconnected O2 got it fixed - finally, but I've missed my appointment with the tax officer...
Just a funny side note: Some years ago O2 had and identical problem with one HLR. However, these days the network architecture was slightly different to today's and the network was designed that - if an HLR would be lost - the data would be transferred to another one. In general it was a clever fallback solution. Unfortunately the second HLR, which was used for this fallback ran on around 80 % capacity which means it wasn't able to handle all the data, coming from first HLR. The result was that also the second HLR dropped out and the traffic from the first and now the second also was transferred to the third. You know what happened? Yes, it dropped out as well 8O and the traffic of 3 dropped out HLRs were on its way to the fourth HLR... It was a real chain reaction! Well, anyone in the network management center was clever enough to press the "emergency stop" key to protect the other HLRs from dropping as well!
However, these days, O2 had serious problems to get the dropped HLRs back to live because in the moment they rebooted it, all the traffic from the previously dropped HLRs pitched on this HLR again with the result the HLR failed again!
So a good advice from me: if you have the feeling that your network has serious problems, it's a good idea to switch off your mobile phone. This will makes it easier for the carrier to get the network back alive fast. It's enough if you check every hour or so if it is working then. Please, never let your cellphones in search mode if a network fails to serve you a service!
Cheers ~ Arne