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shmmax(5)							     shmmax(5)

NAME
       shmmax - maximum size (in bytes) for a System V shared memory segment

VALUES
   Default
   Allowed values
DESCRIPTION
       Shared  memory is an efficient InterProcess Communications (IPC) mecha‐
       nism.  One process creates a shared memory segment and attaches	it  to
       its  address  space.   Any  processes  looking to communicate with this
       process through the shared memory segment, then attach the shared  mem‐
       ory  segment  to	 their	corresponding  address	spaces	as well.  Once
       attached, a process can read from or write to the segment depending  on
       the permissions specified while attaching it.

       This  tunable  sets the maximum size for such a segment within the sys‐
       tem, and is dynamic as of HP-UX 11i.

   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?
       should be raised if it is below	the  maximum  and  user	 programs  are
       attempting  to segments larger than the current value, and receiving an
       error message.

   What Are the Side Effects of Raising the Value?
       The only effect is that user programs can use to get larger segments.

   When Should the Value of This Tunable Be Lowered?
       If you wish to enforce behavior on the user's code, limiting the	 maxi‐
       mum size of System V segments.

   What Are the Side Effects of Lowering the Value?
       None.

   What Other Tunable Values Should Be Changed at the Same Time?
       and  should  be considered because enforcing smaller segments may cause
       the user's code to try to create more segments to accomplish the task.

WARNINGS
       All HP-UX kernel tunable parameters are release specific.  This parame‐
       ter  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  val‐
       ues.  For information about the effects of installation on tunable val‐
       ues, 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
       shmem(5), shmmni(5), shmseg(5).

			   Tunable Kernel Parameters		     shmmax(5)

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