To IPL a mainframe shouldn't take more than five to ten minutes.
and this is totally unacceptable as BA have found to their severe cost. Whoever took the decision to implement a system where recovery is to IPL and blow the reservations system out of the water with no failover needs to take the long walk.
To call the latest crop of "big servers", mainframes, is blatant misrepresentation. True fault tolerant mainframes no longer really exist.
30 Years ago, I ran a demonstration in Paris for airline CIO's and IT Directors, of multi-host file sharing across duplicate mainframes, where it was proved that on catastrophically failing one mainframe, the end result was not one transaction being lost anywhere between the reservations terminal and the failing computer memory module. The impact on the reservations clerk was a "wait" screen that lasted around 40 seconds. The solution sold, but not to BA.
There is absolutely no excuse, 30 years later, for any airline reservations department to accept anything less.
Some very big heads must roll.
Imagegear.