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Full Discussion: Shared memory shortage but lots of unused memory
Top Forums UNIX for Advanced & Expert Users Shared memory shortage but lots of unused memory Post 56864 by cjcamaro on Wednesday 13th of October 2004 02:10:42 PM
Old 10-13-2004
Shared memory shortage but lots of unused memory
I am running HP-UX B.11.11.


I'm increasing a parameter for a database engine so that it uses more memory to buffer the disk drive (to speed up performance). I have over 5GB of memory not being used.

But when I try to start the DB with the increased buffer parameter I get told.

"Not enough Shared Memory"

I am told that there is a Kernel paramater that I need to adjust so that I can use that "unused" memory for this DBs startup.

Does anyone know the kernel parameter that will allow me to use more of my available memory as shared memory?

Chris.
 

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LEARN ABOUT HPUX

max_mem_window

max_mem_window(5)						File Formats Manual						 max_mem_window(5)

NAME

       max_mem_window - maximum number of group-private 32-bit shared memory configurable by users

VALUES

   Default
   Allowed values
DESCRIPTION

       Processes  in  a  PA-RISC 32-bit architecture usually share the global quadrants 3 and 4 for such things as I/O mappings, shared libraries,
       shared mapped files, and so on.	However, you may wish to use quadrant 3 in a more limited sharing fashion with only a select group of pro-
       cesses.	Memory windows allow this functionality.

       If  this tunable is set to 32-bit programs always use the global Q3 and Q4 for shared memory.  If this tunable is greater than processes in
       defined groups use a Q3 private to that group, and then the globally shared Q4 if Q3 is full.

   Who is Expected to Change This Tunable?
       Anyone.

   Restrictions on Changing
       Changes to this tunable take effect immediately.

   When Should the Value of This Tunable Be Raised?
       This tunable should be raised if more group-private Q3 areas are needed by the users of the system.  Each memory window in active use  will
       require approximately 1Mb of kernel memory.  Windows no longer in use will have this memory reclaimed by the system as is feasible.

   What Are the Side Effects of Raising the Value?
       A little more memory is used in the kernel.

   When Should the Value of This Tunable Be Lowered?
       If  process  groups are not being used, or not being used in the quantity set by the tunable, there is really no point to having this value
       higher than what is actually needed.

   What Are the Side Effects of Lowering the Value?
       The kernel uses a little less memory.  If the value is set to no group-private Q3's are allowed.

   What Other Tunable Values Should Be Changed at the Same Time?
       None.

WARNINGS

       All HP-UX kernel tunable parameters are release specific.  This parameter may be removed or have its meaning changed in future releases	of
       HP-UX.

       Installation  of  optional  kernel  software, from HP or other vendors, may cause changes to tunable parameter values.  After installation,
       some tunable parameters may no longer be at the default or recommended values.  For information about the effects of installation  on  tun-
       able  values,  consult  the documentation for the kernel software being installed.  For information about optional kernel software that was
       factory installed on your system, see at

AUTHOR

       was developed by HP.

SEE ALSO

       getmemwindow(1M), setmemwindow(1M), services.window(4).

							     Tunable Kernel Parameters						 max_mem_window(5)
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