CSYSMAS@UCLAMVS.BITNET (Michael Stein) (10/27/89)
As long as you're talking (and reading?) the Principles of
Operation see the section titled "sequence of storage
references".
Disclaimer: This is my favorite section.
This section describes what happens when multiple CPUs or
channels reference the same storage locations. The cases it
defines as having "undefined" results are especially important.
A good understanding of this section is vital to correctly
referencing storage while another CPU or channel might also
reference it. This INCLUDES the use of CS/CDS as well as the
rest of the instructions.
I've only read it 20-30 times over a 10-15 year period of
programming and don't yet have a "good understanding".
PS: This is not important if you are only going to write stuff to
run under CMS as a normal user. It does apply to programs on
MVS systems (especially if you use multitasking and run on a
multiprocessor).