shmem(5) File Formats Manual shmem(5)NAME
shmem - enable or disable System V shared memory
DESCRIPTION
The tunable is obsolete. The System V IPC shared memory subsystem is always enabled.
Shared memory is an efficient InterProcess Communications (IPC) mechanism. One process creates a shared memory segment and attaches it to
its address space. Any processes looking to communicate with this process through the shared memory segment, then attach the shared memory
segment to their corresponding address spaces as well. Once attached, a process can read from or write to the segment depending on the
permissions specified while attaching it.
WARNINGS
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 shmmax(5), shmmni(5), shmseg(5).
Tunable Kernel Parameters shmem(5)
Check Out this Related Man Page
core_addshmem_read(5) File Formats Manual core_addshmem_read(5)NAME
core_addshmem_read - determines the inclusion of readable shared memory in a process core dump
VALUES
Failsafe
Default
Allowed values
or
DESCRIPTION
The tunable was added in response to a problem where a customer was limited in debugging a user-level process crash because shared memory
segments were not written as part of the core file.
Upon core dump, the sections of user memory labeled as shared read-only are written (along with the normal data sections) if this tunable
is set to and left out if it is set to
Who is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect immediately.
When Should the Value of This Tunable Be Raised?
When you wish to include read-only shared memory segments in user core files due to debugging needs by developers or maintainers on the
system.
What Are the Side Effects of Raising the Value?
User process core files would increase in most cases (most applications use at least some shared memory). This could be a problem on sys-
tems where disk space is at a premium.
When Should the Value of This Tunable Be Lowered?
When there is no need for debugging core files where shared memory corruption or data values are in question.
What Are the Side Effects of Lowering the Value?
Core files will tend to be smaller.
What Other Tunable Values Should Be Changed at the Same Time?
Certainly think about which does the same thing for read/write shared memory segments.
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.
Tunable Kernel Parameters core_addshmem_read(5)
I need to create a shared library to access an in memory DB. The DB is not huge, but big enough to make it cumbersome to carry around in every single process using the shared library. Luckily, it is pretty static information, so I don't need to worry much about synchronizing the data between... (12 Replies)
I am fairly new to HP-UX and trying to get a better understanding of the operating system. While poking around a bit I find myself questioning whether I should be concerned about Shared Memory segments with missing CPID and LPID? For example:
ipcs -mp
IPC status from /dev/kmem as of Mon Mar... (2 Replies)
hi
I had to create a shared memory segment which allows the creation of 8 child processes each with 1024 bytes and contains a common buffer area of 2096bytes.
i was able to create the shared memory with shm_open() followed by ftruncate() and mmap() system calls.
but for the shared buffer, i... (3 Replies)
Hi,
I'm currently working on a project to help the analysis of malware from inside the kernel to avoid any kind of detection.
So I need to be able to read the process memory from my kernel module.
As of now, I'm stuck at converting a virtual memory address (for example 0x080483e8 found... (3 Replies)
I'm not an HP-UX Admin professional, but rather a Lawson ERP installer. I'm looking for clues on how to troubleshoot this issue. I have WAS 6.1 ND running on HP-UX 11.23 PA-RISC with the Lawson ERP application . When I start the Lawson application, no errors arise. When I start WAS app server, an... (4 Replies)
Hello ,
I would like to know how to check if a given process id belongs to particualr shared memory segment .
Please help
Thanks in advance (3 Replies)
I mean, I malloc a segment of memory, maybe 1k maybe 20bytes.. assume the pointer is pMem How can I know the content pMem refered is all Zero or \0 . I know memcmp but the second parameter should another memory address... thanx (4 Replies)
Hi,
Basically I've written a game in ncurses that supports multiple players. Each player has a process associated with him which shares a segment of memory in which the player's structures are stored, and these structured are accessed by the 'server' program and handled there. The scope of the... (13 Replies)
Hi all,
I have been working on shared memory. I have created the shared memory and a linked list of 5 nodes. Now I want to attach the linked list to shared memory. When we attach a shared memory it returns a void pointer, but here I am in a fix , how to relate this void pointer to linked list.... (4 Replies)
Is there some way to tell what processes are attached to a shared memory segment? We have a system on which I perform "icps -ma" and there are several segments pending deletion having numerous processes attached to them and I can't tell what processes they are. Neither the creator's pid nor last... (7 Replies)
Hello everyone,
How to connect hash table with shared memory?.I need to update and retrieve data from the shared memory through hash table.
Thanks in advance (13 Replies)
I would be taking my masters degree project next year. So I am now in the process of thinking something that could help me get more in depth knowledge and will be a useful one in practice.
I have thought about creating shared file system for clustered environments (like GPFS,GFS).
I have... (4 Replies)
i have to shared a variable between two different c programs with shared memory and i do these:
int main() {
int a=5,b=7;
int buffer;
int *point;
int shmid;
shmid=shmget(IPC_PRIVATE , sizeof(buffer),0666);
point=(int *)shmat(shmid,NULL,0);
point=a;
... (21 Replies)
Hello
There are options / commands to check which process is consuming maximum memory
However is there any command/mechanism which will tell us which process was consuming maximum memory in specific time interval in the past?
I heard nmon report can help in this regard.
is there any... (5 Replies)
We have several dozen Redhat 5, 6 and 7 servers that are running Oracle databases. On some databases we are using automatic memory management, which uses shared memory. On other databases we are use manual memory management, which does not use shared memory.
When I see that a server is swapping... (2 Replies)