NAME
nflocks — maximum number of file locks
VALUES
Default
The default value is computed at runtime and depends on the amount of physical memory on the system.
For small memory systems (less than 1GB), the default is 1200.
For systems with more than 1GB of memory, the default is 4096, or 4K.
Allowed values
The minimum value is 50. The maximum value is 0x1000000.
Specify a positive integer value.
DESCRIPTION
The
nflocks
tunable represents the maximum number of file locks
that are available system-wide.
Who Is Expected to Change This Tunable?
This tunable should be changed on systems expected to run applications with large number of file locks.
When changing this number note that one file may have several locks,
and databases that use
lockf()
or
fcntl()
may need an exceptionally large number of locks.
Restrictions on Changing
This tunable is dynamic (tuning will take effect immediately on the running system).
When the value of
nflocks
is dynamically tuned it cannot be set to a value lower than the
current number of file locks in the running kernel.
When Should the Value of This Tunable Be Raised?
The value should be increased when large numbers of file locks are expected to be used
simultaneously.
What are the Side Effects of Raising the Value?
The kernel allocates a portion of memory proportional to the new value of
nflocks
and frees memory proportional to the old value.
Additional memory is consumed as new locks are created.
When Should the Value of This Tunable Be Lowered?
The value can be lowered to limit the number of available file locks on a system
and reduce memory consumption.
What are the Side Effects of Lowering the Value?
The kernel allocates a portion of memory proportional to the new value of
nflocks,
and frees memory proportional to the old value.
Additional memory may be released to
the system to be used for other purposes if the usage was ever higher than this new value.
What Other Tunable Values Should Be Changed at the Same Time?
None.
WARNINGS
Setting
nflocks
to the maximum value (0x1000000) will result in a large memory
allocation (~.5GB). A request to change the value of
nflocks
will fail with
ENOMEM
set if there is either not enough free memory or the
remaining free memory would be so small as to potentially hinder system
performance.
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 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.
AUTHOR
nflocks
was developed by HP.
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