BTAM AUTOPOLL CHANNEL PROGRAMS If an operating system is executing BTAM channel programs, VM/370 checks
each BTAK autcpoll CCW string to see if it has been dynamically changed.
It does this each ti.e the string is executed. To bypass this checking,
issue the CP command:
set autopoll on Whenever the BTAM autopoll CCWs are .odified, OS/VS1 Release 6 and DOS/VS Release 34 with the Advanced Functions-DOS/VS program Product
(Program NO. 5746-XE2) use the DIAGNOSE instruction code X'28' to notify VK/370. The combination of the SET AUTOPOLL ON command and the use of the
diagnose interface reduces VM/370 overhead and improves the overall
performance for that particular user. However, both of these facilities aust be active.
If a user has specified SET AUTOPOLL ON and the operating system does
not use the diagnose interface, a channel program modification goes
undetected. The results are unpredictable.
If a user has specified SET AUTOPOLL OFF and the operating system
uses the diagnose interface, the unnecessary checking results in
performance degradation. !gte: Set DOS/VS AUTOPOLL on when using VM/VS handshaking.
8 VM/370 operating Systems in a Virtual Machine
Special Considerations for Multiprogramming
Systems under VM/370 When a multiprogramming operating system such as OS/VS or DOS/VS is run
in a virtual machine, its resource-management algorithms interact with
those of VM/370 -- especially when the virtual operating system has a page wait or an I/O wait. Multiprogramming operating systems use these
two methods to interact with VM/310: VM/VS handshaking The diagnose interface
This topic discusses these methods and
an operating system under VM/370 that
situations. VM/VS HANDSHAKING also those aspects of running
apply only in certain unique VM/VS handshaking permits instructions issued by an operating system in
a virtual machine to be processed directly by the processor. It also permits VM/310 to simulate privileged instructions. VM/VS handshaking
is available for these operating systems running in virtual machines
under VM/370: DOS/VS Release 34 with the Advanced Functions-DOS/VS Program Product (S746-XE2) DOS/VSE with the VSE/Advanced Functions Program Product (5746-XES) VS1 Release 4 and subsequent releases DOS/VS Release 34 with the Advanced Functions-DOS/VS program Product (S746-XE2) uses handshaking. The use and efficiency of DOS/VS with handshaking is similar to VS1. For further details, refer to the
appropriate DOS/VS program product publications. DOS/VSE with the VSE/Advanced Functions program Product (5146-XES) uses VM/VS handshaking (also known as the DOS/VSE-VM/370 linkage
facility). The use and efficiency of DOS/VSE with handshaking is similar to VS1. For further details, refer to GC33-6106. Although handshaking is a system generation feature for 'Sl, it is
active only when VS1 is under the control of VM/370. It is disabled
when that same iS1 operating system is run on a real machine. For
details about VM/yS handshaking for VS1, refer to the "OS/VS in a
virtual Machine" section in this publication. Section 1. General Considerations 9
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