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Full Discussion: Installed memory ≠ usable size?
Special Forums Hardware Filesystems, Disks and Memory Installed memory ≠ usable size? Post 302331719 by otheus on Tuesday 7th of July 2009 04:17:02 AM
Old 07-07-2009
Quote:
But if I could address 48 bits, that wouldn't be a problem. Right?
You have only 4 GB of RAM installed. You can't get more RAM than what you have installed. If the OS sees 3.5 GB, it correctly sees how much is physically available to it.

A single process will have only 2 GB available to it unless you install some kernel patches which move the shared-memory boundary. On the other hand, if you use shared memory (for postgres, oracle, maybe mysql, large virtual ram disk), you can utilize all of the memory currently in your system.

If you want to expand another gigabyte or so, you'll need PAE or a 64-bit OS.
 

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LEARN ABOUT HPUX

core_addshmem_write

core_addshmem_write(5)						File Formats Manual					    core_addshmem_write(5)

NAME

       core_addshmem_write - determines the inclusion of read/write shared memory in process core dump

VALUES

   Failsafe
   Default
   Allowed values
       or

DESCRIPTION

       The  tunable  was added in response to a problem where a customer was limited in debugging a user-level process crash because shared memory
       segments were not written as part of the core file.

       Upon core dump, the sections of user memory labeled as shared read-write are written (along with the normal data sections) if this  tunable
       is set to and left out if it is set to

   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?
       When  you  wish	to include read-write shared memory segments in user core files due to debugging needs by developers or maintainers on the
       system.

   What Are the Side Effects of Raising the Value?
       User process core files would increase in most cases (most applications use at least some shared memory).  This could be a problem on  sys-
       tems where disk space is at a premium.

   When Should the Value of This Tunable Be Lowered?
       When there is no need for debugging core files where shared memory corruption or data values are in question.

   What Are the Side Effects of Lowering the Value?
       Core files will tend to be smaller.

   What Other Tunable Values Should Be Changed at the Same Time?
       Certainly think about which does the same thing for read-only shared memory segments.

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.

							     Tunable Kernel Parameters					    core_addshmem_write(5)
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