maxdsiz(5) File Formats Manual 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 segment 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 memory 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 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
getconf(1), getrlimit(2), setrlimit(2), maxtsiz(5), maxssiz(5).
Tunable Kernel Parameters maxdsiz(5)