fcache_vhand_ctl man page on HP-UX

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fcache_vhand_ctl(5)					   fcache_vhand_ctl(5)

       fcache_vhand_ctl	 - file cache policy control for the system pager dae‐

   Allowed values
   Recommended values
       Default value

       The tunable is used to determine the aggressiveness of the system pager
       daemon  with  respect  to  flushing the file pages from the file cache.
       must be a positive integer between 0 and 10, 0 being the default.

       In general, the system  pager  daemon  behaves  more  aggressively  for
       higher values of A change in the value may have a direct impact on sys‐
       tem throughput and response times.

       If the system pager daemon is not aggressive, less free memory  may  be
       available  in  the file cache, and a file I/O intensive application may
       observe a loss in performance.  If the paging daemon is too aggressive,
       the system may observe thrashing, and the CPU utilization by the system
       pager daemon may increase.

       Customers must evaluate the performance impact in their workload	 envi‐
       ronment	before	changing  the  value  of this tunable from the default
       value on production systems.  To determine a reasonable value  for  you
       should consider the file system I/O-intensive applications on your sys‐
       tem, the I/O responsiveness needed, the I/O  throughput	required,  and
       the permissible CPU utilization by the system pager daemon.

       You  should  also  consider  changes  to and before modifying See file‐
       cache_min(5) and filecache_max(5).

   Who Is Expected to Change This Tunable?
       Administrators investigating the performance  characteristics  of  file
       I/O intensive workloads.

   Restrictions on Changing
       Changes to this tunable take effect immediately.

   When Should the Value of This Tunable Be Raised?
       Confirm	the and values are sufficient for an I/O intensive application
       before raising this tunable.

       The tunable should be raised when  the  system  suffers	from  low  I/O
       responsiveness  of and low I/O throughput.  The tunable should be exer‐
       cised with extreme caution as it will have a direct  impact  on	system
       throughput  and response times.	In most case, the default value should
       be sufficient.

   What are the Side Effects of Raising the Value?
       Increasing the value should increase the CPU utilization of the	system
       pager daemon and may vary the I/O throughput.

   When Should the Value of This Tunable Be Lowered?
       The  tunable  should  be lowered when the system seems to spend most of
       it's time running the the system pager daemon.

   What are the Side Effects of Lowering the Value?
       The I/O responsiveness may decrease and the I/O throughput may vary.

   What Other Tunable Values Should Be Changed at the Same Time?

       An invalid value is entered that is not an integer
		      between 0 and 10, such as a negative number.

       All HP-UX kernel tunable parameters are release specific.  This parame‐
       ter  may	 be  removed or have its meaning changed in future releases of

       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   HP-UX	Release	   Notes    at

       was developed by HP.

       filecache_min(5), filecache_max(5).

			   Tunable Kernel Parameters	   fcache_vhand_ctl(5)

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