maxdsiz(5)maxdsiz(5)NAME
maxdsiz, maxdsiz_64bit - maximum size (in bytes) of the data segment
for any user process
VALUES
Default
Allowed values
DESCRIPTION
User programs on HP-UX systems are composed of five discrete segments
of virtual memory: text (or code), data, stack, shared, and I/O. Each
segment occupies an architecturally defined range of the virtual
address space that sets the upper limit to their size. However, text,
data, and stack segments may have a smaller maximum enforced by the and
tunables.
This tunable defines the maximum size of the static data storage seg‐
ment for 32-bit and 64-bit processes. The data storage segment con‐
tains fixed data storage such as globals, arrays, static variables,
local variables in main(), strings, and space allocated using and
Who is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect only for processes started after
the modification. In addition, a process which modifies its for the
data segment propagates the modified limit to all child processes,
thereby exempting them from any future modification of The value speci‐
fied is expected to be a multiple of the base page size. See the
description of in getconf(1) for more details. If the value specified
is not a multiple of the base page size, it will be rounded down to the
nearest multiple of the base page size.
When Should the Value of This Tunable Be Raised?
This tunable should be raised if user processes are receiving the error
message:
or
This may or may not cause a process failure depending on the program
code.
What Are the Side Effects of Raising the Value?
Raising this tunable by definition allows larger data segments for
every process. This means that and function as limitations on the
amount of swap space that can be reserved or used by each process.
Therefore, using more virtual address space does not translate directly
into using more physical address space because virtual pages can be
swapped out.
If swap space on the machine is near capacity, raising this tunable
increases the amount of reservable swap per process. This could
exhaust the swap space on the system by allowing a process with a mem‐
ory leak or a malicious program that uses huge amounts of memory to
reserve too much swap space.
When Should the Value of This Tunable Be Lowered?
This tunable should be lowered if swap space is at a premium on the
machine and programs that are using too much swap space are affecting
the execution of other critical user processes.
What Are the Side Effects of Lowering the Value?
If swap space on the machine is near capacity, lowering this tunable
will limit the amount of swap reserved for each process and will cause
the processes that consume large amounts of swap space to receive the
error.
What Other Tunable Values Should Be Changed at the Same Time?
The tunable should be considered because it also limits swap usage by
process stack segment.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parame‐
ter 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 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
AUTHOR
was developed by HP.
SEE ALSOgetconf(1), getrlimit(2), setrlimit(2), maxtsiz(5), maxssiz(5).
Tunable Kernel Parameters maxdsiz(5)