fcache_seqlimit_system man page on HP-UX

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fcache_seqlimit_system(5)			     fcache_seqlimit_system(5)

       fcache_seqlimit_system  - percentage of file cache that can be consumed
       by sequential accesses, per system-wide limit

   Allowed values
       The minimum value allowed is The maximum value allowed is

       Specify a positive integer value.

       This parameter places a system-wide limit on how	 much  memory  can  be
       consumed	 in the file cache by sequential accesses.  It is important to
       note the relationship between this tunable and the per-file limit  tun‐
       able,  These  two  tunables, in conjunction, control how much memory in
       the file cache can be consumed by sequential accesses.

       When sequential accesses to a file has exceeded the per-file limit  AND
       the system-wide limit, the excess file cache pages are paged out.  Note
       that both limits have to be reached  in	order  for  page  stealing  to
       occur.	For  example, a file can exceed its limit if the limit has not
       been reached.  Similarly, no page stealing occurs if none of the	 files
       on  the system has exceeded the per-file limit, even if the system-wide
       limit has been hit.

       The page stealing feature is specific to improving sequential I/O  per‐
       formance for large files.  Limiting file cache memory consumption helps
       alleviate memory pressure in the file cache.  It	 also  prevents	 cache
       wiping  -- a single thread sequentially accessing a large file can wipe
       out the existing contents of the file cache.

   Who is Expected to Change This Tunable?
       System administrators that run applications which do  large  sequential
       file  I/O's.  Typically, these files are larger than the size of physi‐
       cal memory on the system.

   Restrictions on Changing
       Changes to this tunable take effect immediately.

   When Should the Value of This Tunable Be Raised?
       When you wish to allow greater file cache consumption due to sequential
       accesses.   Setting  and	 to  100  effectively  disables the sequential
       access page stealing feature.

   What Are the Side Effects of Raising the Value?
       Setting the tunable too high  may  yield	 poor  performance  for	 large
       sequential  I/O's  for  large files (larger than physical memory size).
       and should be tuned appropriately for the anticipated workload.

   When Should the Value of This Tunable Be Lowered?
       When you wish  to  limit	 file  cache  consumption  due	to  sequential
       accesses.   Setting  and to 0 forces sequential access page stealing to
       always occur.

   What Are the Side Effects of Lowering the Value?
       Could cause more pageouts to occur in an	 attempt  to  limit  the  file
       cache consumption.

   What Other Tunable Values Should Be Changed at the Same Time?
       and should be changed at the same time.

       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 at

       was developed by HP.


			   Tunable Kernel Parameters fcache_seqlimit_system(5)

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