There used to be, probably still is, a limit on the total number of
extents for all PDS libraries in the Linklist. If adding one more
extent to a Linklist library would put you over that limit, a failure
would occur at the next Llinklist rebuild. Because of this, some on
this list have in the past advocated against allowing secondary extents
for any Linklist libraries. Every once in a while I would get concerned,
count our total extents, and always found we were less than 50% of the
max. I suspect hitting that max would be unlikely for many
installations; but if you were one of those installations at risk, then
it would make sense to avoid Linklist secondary allocations or at least
police them closely. For the rest of us, having multiple extents in
Linklist libraries may be an indication of an under-allocated library
and may be aesthetically displeasing, but is OK as long as you aren't
about to exhaust a PDS directory space as well.
On the other side, if you have a bad module in a full, actively used
linklist library that cannot be safely compressed and the module must be
replaced in order for the system to run correctly after the next IPL,
having the ability to dynamically allow another extent to the library
and install a module that will not be seen until the next Linklist
creation was always better than not being able to install the module at
all. There are always alternatives, like allocating a new library with
a different name and changing the Linklist definitions to use that, but
that is a more complex solution requiring additional changes and with
additional opportunity for error -- best reserved for cases where a
rebuild of the library is really required.
Joel C. Ewing
On 08/10/2014 06:05 AM, Charles Mills wrote:
> I get your first point -- makes sense.
>
> But is your third sentence garbled? Why should it [multiple extents?] be a
> problem for non-linklist libraries at the next IPL? Or am I mis-reading your
> sentence?
>
> Charles
> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:[email protected]] On
> Behalf Of Bob Shannon
> Sent: Sunday, August 10, 2014 12:53 PM
> To: [email protected]
> Subject: Re: Extents more than One for load modules library
>
>> Load libraries go to more than one extent all the time. I don't believe
>> there is any "general" problem.
>
--
Joel C. Ewing, Bentonville, AR [email protected]
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