abnormal termination of user tasks (abend) and response degradation.
Errors that are successfully retried or corrected are known only to theI/O supervisor and the I/O error retry and recording routines; they
appear to the second level interruption handlers (such asWAITP1GE) as
if the original operation completed normally.SOFT
considered to be a soft error.DMKPTRAN calls DMKPGTPG to assign a
differentDASD page slot and the page is re-queued for output. The slot
that caused the error is not de-allocated, and thus is not assigned to
another virtual machine. All other uncorrectable paging errors are hard
because theymore drastically affect system performance. RECOVER!: Hard paging errors occur on either I/O errors for
page reads or uponeXhausting the system's spooling and paging space.
Recovery attempted on hard errors depends upon the nature of the taskfor which the read was being done. If the operation was an attempt to
place a page of a virtual machine's virtual storage into real storage,
the operation of that particular virtual machine is terminated by
setting the pageframe in error to zero and placing the virtual machine
in console function mode. The user and operator are informed of the
condition, and the page frame causing the error is not de-allocated,
thereby ensuring that it is not allocated to anotheruser& The control program functions that call DMKPTRAN (such as spooling,
pageable control program calls, andsystem directory management) have
the option of requesting that unrecoverable errors be returned to the
caller. In this case, theCP task may attempt some recovery to keep the
entire systemfrom terminating Cabend). In general, every attempt is aade to at least allow the operator to bring the system to orderly
shutdown if continued operation is impossible.
Proper installation planning should make the occurrence of a space
exhaustion error an exception. An unusually heavy user load and a
backed-up spooling file could cause this to happen. The operator is
warned when90% of the temporary (paging/spooling) space in the system
is exhausted. He should takeimmediate steps to alleviate the shortage.
Possible reaedies that exist include preventingmore users from logging
on and requesting users to stop output spooling operations.More drastic measures might include the purging of low-priority spool files. If the
system's paging space is completely exhausted, the operation of virtualmachines progressively slows as more and more users have paging requests
that cannot be satisfied and operator intervention is required.VIRTUAL RELOCATION CP provides the virtual aachine the capability of using the DAT feature
of the realSystem/370. Programming simulation and hardware features
arecombined to allow usage of all of the available features in the real
hardware, (that is, 2K or 4K pages, 64K or1M segments) • For clarification, soae tera definitions follow: CPU, in which CP resides. machine, maintained by CP. CP Introduction 1-117
Errors that are successfully retried or corrected are known only to the
appear to the second level interruption handlers (such as
if the original operation completed normally.
considered to be a soft error.
different
that caused the error is not de-allocated, and thus is not assigned to
another virtual machine. All other uncorrectable paging errors are hard
because they
page reads or upon
Recovery attempted on hard errors depends upon the nature of the task
place a page of a virtual machine's virtual storage into real storage,
the operation of that particular virtual machine is terminated by
setting the page
in console function mode. The user and operator are informed of the
condition, and the page frame causing the error is not de-allocated,
thereby ensuring that it is not allocated to another
pageable control program calls, and
the option of requesting that unrecoverable errors be returned to the
caller. In this case, the
entire system
shutdown if continued operation is impossible.
Proper installation planning should make the occurrence of a space
exhaustion error an exception. An unusually heavy user load and a
backed-up spooling file could cause this to happen. The operator is
warned when
is exhausted. He should take
Possible reaedies that exist include preventing
on and requesting users to stop output spooling operations.
system's paging space is completely exhausted, the operation of virtual
that cannot be satisfied and operator intervention is required.
of the real
are
hardware, (that is, 2K or 4K pages, 64K or
