Conference bulova::decw_jan-89_to_nov-90

See Note 586 for global pages per application figures.

Jatin

    Bear in mind the tradeoffs here:
    
    Too few  GS/GP ==> system doesn't work in entirety
    Too many GS/GP ==> system works but uses more memory than required
    
    The rub is that the penalty for "too many" GS/GP is minor.  Costs about
    one real page per 10,000 GBLPAGES, for example.
    
    Shooting for the absolute minimum amount seems to be the wrong tradeoff
    of your time.  Assuming you get to make that decision.
     
      John

    Perhaps I did not make myself clear.
    
    I want to know the number of global sections and global pages that
    DECwindows uses simply by virtue of the fact that it is on your system.
    
    I DON'T CARE how many GS/GP's are used by a DECwindows _APPLICATION_.
    
    A customer wants to set up a VAXstation 2000 and have it run VWS.  He
    could not care less if DECwindows was on his system.  In fact, if
    DECwindows uses up too many resources,  HE'D LIKE TO REMOVE IT!
    
    ....so he wants to know how many GS's and GP's he could save by
    removing DECwindows from his system!
    
    You know how in the Installation Guides for layered products it tells
    you how many GS's and GP's the product requires just to BE on your
    system.  ... THOSE are the numbers he wants for DECwindows.
    
    
    Thanks again!
    Ken

Ken,

The only cost in global pages for having DECwindows installed (but unused) is
for what ever executable and sharable images are installed (using MCR INSTALL).
This should be very small.  The real cost for having DECwindows on your system
and not using it is disk space.

The reason that people were confused is that GPs and GSs are resources that
get used up by running applications not by having them sit around.  So when
faced with a question of how many of these are used by DECwindows, we (or at
least I) assumed you meant running DECwindows applications.

Dick

This seems like a reasonable place to ask this:

Dear DW Developers:

Why does having too few GBLPAGES or GBLSECTIONS cause accvio or other
ignoble crashes?  Why can not DW programs print something more
friendly, like `You need nnn more GBLwhatever to run this application'?

Also, I have suffered server crashes even when I have plenty of GBL* and
when AUTOGEN is happy.  Doing AUTOGENs based on, say, 5 minutes of
*very* heavy use seems to fix this, leading me to believe that other
resources than GBL* are critical to DW.  Can you comment?

Thanks!

I know that .-1 was not addressed to me, but here is a possible answer to why
you may have needed more global pages, even though there were "plenty" avail-
able.

Any one global section can use only contiguous global pages.  If therefore I
try to map a 1000 page global section, and the largest contiguous block of
pages available is only 800, there is nothing that VMS can do but refuse, even
if there are many 1000s available in total.

The easiest way to verify this is to do the following from DCL:
	$ A=F$GetSyi("Free_GblPages")
	$ B=F$GetSyi("Contig_GblPages")
	$ Show Symb A
	$ Show Symb B

If the first value is big enough for your section, but the second is not, then
you have a "fragmentation" problem.  Rebooting will fix it temporarily, but
allocating more global pages is the long-term solution.

(If you know all this already, sorry ...)

T

RE: .-1... No, I didnt know that.  That is usefull information.  It
seems that I usualy have 10,000 to 15,000 gblpages free, but perhaps
if the overhead is so low as is suggested in a previous reply I should
make it so that there are 50,000 to 100,000 free, right?

I am still very curious why the symptom of a lacking of these resources
is an ACCVIO as opposed to a message.  Can't you tell that you don't
have enought when you attempt to allocate them?