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HP-UX Reference > Sshmseg(5)Tunable Kernel ParametersHP-UX 11i Version 2: December 2007 Update |
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NAMEshmseg — maximum number of System V shared memory segments per process 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. Once attached, a process can read from or write to the segment depending on the permissions specified while attaching it. This tunable sets an upper limit to the number of segments which can be attached per process. 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 (shmmni). What Are the Side Effects of Raising the Value?A single process will be able to acquire more segments, possibly starving another process which previously was able to acquire all the segments it needed. In this case, shmmni should be raised if it is below it's maximum. 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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