shmseg(5)shmseg(5)NAMEshmseg - maximum number of System V shared memory segments per process
VALUES
Default
Allowed values
Maximum: Any value less than or equal to
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 memory
segment to their corresponding address spaces. Once attached, a
process can read from or write to the segment depending on the permis‐
sions specified while attaching it.
This tunable sets an upper limit to the number of segments which can be
attached per process.
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?
If user processes reach their limit, more segments are desired, and the
current value is less than the total number of segments in the system
What Are the Side Effects of Raising the Value?
A single process will be able to acquire more segments, possibly starv‐
ing another process which previously was able to acquire all the seg‐
ments it needed. In this case, should be raised if it is below it's
maximum.
When Should the Value of This Tunable Be Lowered?
This tunable should only be lowered to enforce segment policy on user
processes, or if one runaway process is hogging the global-segment
pool. Otherwise, keeping the maximum higher than the common usage is
harmless.
What Are the Side Effects of Lowering the Value?
None.
What Other Tunable Values Should Be Changed at the Same Time?
should be considered, as previously described.
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 ALSOshmmni(5).
Tunable Kernel Parameters shmseg(5)