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sys_attrs_ipc(5)					     sys_attrs_ipc(5)



NAME

  sys_attrs_ipc	- attributes for the ipc kernel	subsystem

DESCRIPTION

  This reference page describes	attributes for the Interprocess	Communication
  (ipc)	kernel subsystem.

  In the following list, attributes whose names	are preceded by	an asterisk
  (*) can be modified at run time as well as at	boot time.

  See sys_attrs(5) for an introduction to system attributes and	how to set
  them.



  max_kernel_ports
      The maximum number of kernel IPC ports that can be used on the system
      at one time.

      Default value: (task-max * 3 + thread_max) + (thread_max * 2) + 2000

      (Values of variables used	to establish default value: task_max = nproc
      +1; thread_max = nproc *2; nproc = 20 + 8	* maxusers)

      Do not modify the	default	setting	for this attribute unless instructed
      to do so by support personnel or by patch	kit documentation.



  msg_max
      Maximum size, in bytes, of a single System V message.

      Default value: 8192 (bytes, which	equal 1	page)

      Minimum value: 0

      Maximum value: INT_MAX

      Values for this attribute	are restricted by the amount of	main memory
      on the system. The minimum value (0) disables the	messaging system.



  msg_mnb
      Maximum number of	bytes that can be queued to a single System V message
      queue.

      Default value: 16,384 (bytes, which equal	2 pages)

      Minimum value: 0

      Maximum value: INT_MAX

      Values for this attribute	are restricted by the amount of	main memory
      on the system. The minimum value (0) disables the	messaging system.



  msg_mni
      Maximum number of	System V message queues	that can be used on the	sys-
      tem at one time.

      Default value: 50	(queues) The system rounds the number to the value
      associated with the next higher power of two; for	example, 64.

      Minimum value: 0

      Maximum value: INT_MAX

      Values for this attribute	are restricted by the amount of	main memory
      on the system. The minimum value (0) disables the	messaging system.



  msg_tql
      Maximum number of	messages (system wide) that can	be queued to System V
      message queues at	one time.

      Default value: 40	(messages)

      Minimum value: 0

      Maximum value: INT_MAX

      Values for this attribute	are restricted by the amount of	main memory
      on the system. The minimum value (0) disables the	messaging system.



  sem_aem
      A	value that controls the	maximum	adjustment that	can be made to any
      System V semaphore when a	process	exits.

      Default value: 16,384

      Minimum value: 0

      Maximum value: 65,536



  sem_mni
      Maximum number of	System V semaphores that can be	used on	the system at
      one time.

      Default value: 10	 (semaphores) (The system rounds the number to the
      value associated with the	next higher power of two; for example, 16.)

      Minimum value: 0

      Maximum value: INT_MAX



  sem_msl
      Maximum number of	System V semaphores that can be	used by	a single pro-
      cess at one time.

      Default value: 25	(semaphores)

      Minimum value: 0

      Maximum value: INT_MAX



  sem_opm
      Maximum number of	operations that	can be outstanding on a	single System
      V	semaphore at one time.

      Default value: 10	(operations)

      Minimum value: 0

      Maximum value: INT_MAX



  sem_ume
      Maximum number of	undo operations	that can be outstanding	on a single
      System V semaphore at one	time.

      Default value: 10	(operations)

      Minimum value: 0

      Maximum value: INT_MAX



  sem_vmx
      Maximum integer value that any System V semaphore	can contain.

      Default value: 32,767

      Minimum value: 0

      Maximum value: INT_MAX, but do not enter values higher than 65535



  * shm_allocate_striped
      A	value that sets	default	policy for shared memory allocation on NUMA-
      enabled systems (GS80, GS160, GS320). A value of 1 means that shared
      memory is	striped	across Resource	Affinity Domains (RADs). A value of 0
      means that shared	memory is not striped across RADs.

      Default value: 1

      Although you can change the value	of this	attribute while	the system is
      running, there are currently no known situations for which the
      shm_allocate_striped value should	be changed. A value of 1 is the
      recommended default policy for all applications on NUMA-enabled sys-
      tems. Furthermore, changing the value to 0 on these systems does not
      override use of striped memory allocation	by applications	that expli-
      citly specify and	control	it through NUMA-specific programming inter-
      faces.

      This attribute has no effect on platforms	that do	not use	NUMA archi-
      tecture.

      See numa_intro(3)	for an introduction to NUMA.



  shm_enable_core_dump
      Disables (0) or enables (1) the dumping of shared	memory regions to the
      core file.  The attribute	is only	used in	conjunction with shared
      memory.

      Default value: 1 (on).



  shm_max
      Maximum size, in bytes, of a single System V shared memory region.

      Default value: 4,194,304 (bytes) (This value equals 512 pages)



  shm_min
      Minimum size, in bytes, of a single System V shared memory region.

      Default value: 1 (All requests are rounded to the	next page size.)



  shm_mni
      Maximum number of	shared memory regions that can be used on the system
      at one time.

      Default value: 100 (regions) (The	system rounds the number to the	value
      associated with the next higher power of two; for	example, 128.)



  shm_seg
      Maximum number of	System V shared	memory regions that can	be attached
      to a single process at one time.

      Default value: 32	(regions)



  * ssm_enable_core_dump
      If enabled (1), writes segmented shared memory contents when an appli-
      cation issues a core dump. If disabled (0), segmented shared memory is
      not written to the core dump.

      Default value: 1 (enabled)

      Because segmented	shared memory can be  large, the amount	of time
      needed to	dump the region	to a core file and the amount of file system
      space required by	the operation can be extensive,	especially in large
      database environments.  Therefore, although shared memory	can be useful
      for debugging, you may not want to include it in core files because of
      time and resource	limitations.

      This attribute can be modified at	run time.



  * ssm_threshold
      The minimum size,	in bytes, of a System V	shared region for the use of
      shared page tables.  Setting this	value to 0  disables the use of
      shared page tables for shared memory. The	size must be at	least equal
      to the value of SSM_SIZE,	which is  defined in the machine/pmap.h	file
      (the default is 8	MB).

      This attribute can be modified at	run time.

      Default value: SSM_SIZE

      Minimum value: SSM_SIZE

SEE ALSO

  sys_attrs(5)

  System Configuration and Tuning