December 2006
Intermediate to advanced
228 pages
6h 20m
English
book
Introduction to the New Mainframe: Large-Scale Commercial Computing
by Mike Ebbers, Pilar Gonzalez Adrados, Frank Byrne, Rodney Martin, Jon Veilleux
Content preview from Introduction to the New Mainframe: Large-Scale Commercial Computing
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114 Introduction to the New Mainframe: Large-Scale Commercial Computing
6.5 Mapping for access to devices
This document does not cover the internal operation of the z/OS platform.
However, it simplifies the following topics to briefly mention three elements,
referred to as
control blocks. These are the Unit Control Block (UCB), the Unit
Control Word (UCW) and the Control Unit Control Block (CUCB), as explained in
more detail here:
UCB The UCB is used by z/OS to represent every device that may be used
for an I/O operation. It contains state information and queues of
requests to access the device.
UCW The UCW is equivalent to the UCB in representing ...
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