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HP-UX Reference > Sshmmax(5)Tunable Kernel ParametersHP-UX 11i Version 2: December 2007 Update |
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NAMEshmmax — maximum size (in bytes) for a System V shared memory segment DESCRIPTIONShared memory is an efficient InterProcess Communications (IPC) mechanism. 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 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 system, and is dynamic as of HP-UX 11i. When Should the Value of This Tunable Be Raised?shmmax should be raised if it is below the maximum and user programs are attempting to shmget segments larger than the current value, and receiving an EINVAL error message. What Are the Side Effects of Raising the Value?The only effect is that user programs can use shmget to get larger segments. WARNINGSAll 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 tunable values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see HP-UX Release Notes at http://docs.hp.com. |
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