fcache_seqlimit_system(5)					File Formats Manual					 fcache_seqlimit_system(5)

NAME

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

VALUES

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

       Specify a positive integer value.

DESCRIPTION

       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 tunable, 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 sys-
       tem-wide limit has been hit.

       The page stealing feature is specific to improving sequential I/O performance 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 phys-
       ical 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.

WARNINGS

       All 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  tun-
       able  values,  consult  the documentation for the kernel software being installed.  For information about optional kernel software that was
       factory installed on your system, see at

AUTHOR

       was developed by HP.

SEE ALSO

       fcache_seqlimit_file(5).

							     Tunable Kernel Parameters					 fcache_seqlimit_system(5)