shmmax(5)shmmax(5)NAMEshmmax - 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 ALSOshmem(5), shmmni(5), shmseg(5).
Tunable Kernel Parameters shmmax(5)