El 01/10/2013, a les 0:40, Dave McGuire <mcguire at neurotica.com> va escriure: As (primarily) UNIX people, we are trained to think in terms of abstraction layers and common interfaces. The IBM mainframe world in general, and JCL in particular, find no value at all in that. Production shops today, on modern hardware, still sometimes think in terms of allocating cylinders on disk drives for job output. Not 'sometimes'. Most of times. A IBM educated programmer misses the possibility of limiting the output storage used by a program. The idea of a runaway program eating a whole filesystem is... weird. On the other hand, the 'file' concept is abstract in MVS. The programmer uses 'files' which are bound to real physical datasets via JCL, so there is some level of abstraction at the I/O level. VMS and RSX 11M+ have the logical name stuff, which can be seen as similar to the DD cards in a job. Unfortunately UNIX dies not have anything similar (symlinks being the closest ). JCL is fast to parse, efficient to execute, and hard to read and write. Most of the JCL is generated automatically from skeletons or put together by a program. It is a little bit hard to code JCL by hand, but it is really easy to write a JCL generator. The IBM mainframe world never bought into that bullshit idea of "programmer time is more important than processor time", because, well, it isn't. The programmer does whatever is fastest for the computer to execute. Well, the damn subcapping thing makes an installation to be very aware about CPU usage. And, one way or another, IBM always wins this war... -Dave -- Dave McGuire, AK4HZ New Kensington, PA