It’s 1979, and a big university hospital depends on this mainframe in its data center, according to an IT pilot fish who works there.

“Every building in the mile-wide complex was tied to the IBM System/370-148 computer running DOS/VSE,” says fish. “We had IBM printers as well.

“One day, one of the very best IBM techs was called in to work on one of the printers. He needed a ‘P 00E’ command issued so he could work on that printer. But instead he requested a ‘DVCDN 00E’ command — which removes all the system assignments to that device.”

Fish keys in the command that the tech requests. The mainframe crashes.

He tries to restart the big machine, but that fails almost immediately. Turns out that the second command in the startup sequence is one that directs output to the printer known as 00E — which the mainframe no longer knows how to use.

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