The Question is:
What exactly is a bad page and will I always see bad pages when I do the show
Does it matter if they are Dynamic, I/O Errors, or Static?
The Answer is :
A bad page is usually a hardware failure within the memory system,
but can also be an indication of what is known as a memory hole --
memory holes typically only appear when certain memory hardware
configurations are used in conjunction with old OpenVMS releases
(qv V6.2-1H3) and combine to produce gaps within the physical
address space. These gaps or holes are identified as bad pages.
In cases where these bad pages are the result of memory holes,
these are largely harmless -- these memory holes result from
unsupported system configurations. Most commonly, these involve
the Alphaerver 4100 series and related platforms, as these are
among the earliest platforms where memory holes could exist.
Resolution involves reconfiguring or removing memory, or upgrading
to a more recent OpenVMS release, or wasting the physical memory
needed for the data structures used to track these bad pages.
From the OpenVMS Alpha V6.2-1H3 release notes:
1.6.3 Memory Restriction
The OpenVMS Alpha Version 6.2-1H3 operating system does not
efficiently support physical memory holes. The operating
system assumes that physical memories are contiguous
and, as a result, creates certain non-pageable memory
management structures that are larger than they need to
be. This problem will be addressed in a future version of
the operating system. Until then, Digital recommends that
you avoid configuring systems in this manner.
In cases where these bad pages indicate an underlying hardware
error, these errors are normally isolated by OpenVMS. The pages
of memory reporting the error(s) are rendered inaccessable.
The resolution of these bad pages normally requires a hardware
Please contact your hardware support organization for assistance
in determining the specifics of the bad page(s0 you are seeing,
Expect to be asked details of the reported bad pages, about the
system model, and any relevent details from the system error
For additional information on the AlphaServer 4100 series and
bad pages that can result from memory holes, please see (9935).