Use sysdef to see current limits, e.g.
then modify /etc/system (and reboot) to set your limits as per the Oracle installation documentation, for example:
Cheers
ZB
Hi all,
we have been noticed that few of processes failed with no reason.
when I chcked the log messages, I have got the following error messages writen to ktlog
just a few minutes before!
When the kernel writes such warning meassages?
will the system sends/generates any signals like... (1 Reply)
Hi all,
I am running 7.3 Redhat Linux, I have Oracle database running on it and I have some problem with the memory. every time I startup the database, the memory was peak up to 630M of Ram out 640M ram on the entire box and I didn't specify that much of memory on my database. Oracle advise me... (2 Replies)
Received the following on the weekend.
Panic:k_trap kernel mode trap type 0X0000000e cannot dump 163739 pages to dumpdev hd (1/41):space for only 48640 pages
Dump not complete
Safe to power off or press any key to reboot
Any ideas how to fix this one? It also happen a month ago. (3 Replies)
Hello!
Does anyone know howto reload your kernal without rebooting the machine?
I´ve updated the "/etc/security/limits.conf " file and need to make this active without rebooting the machine. this is Red Hat Advanced Server 2.1AS
Regards...
dOzY (3 Replies)
hello all,
as we know that the kernal Schedules tasks with some time slice given to each.
how does the Kernal know that the time of a Task has been elapsed?
does it follow the syatem Clock?or how?
thanks for your time (4 Replies)
hi,
can anybody tell me how to increase the parameters like project.max-shm-ids on solaris10.
i have used prctl, but got reset while server reboot.
thnks and regards
Ajay (1 Reply)
I am trying to restore Unixware 7.1 from a backup using RestoreEdge which is from Microline version 2. The restore is on another machine using the same RAID controller and TBU. We are retiring the other machine.
Anyway, we get to disk #2 and it panics. Here is the Pic.
Can anyone tell me... (13 Replies)
Hi,
Can you please let me know about kernal parameters?
Where we can see that kernal parameters?
we are using System = SunOS 5.10.
Please let me know commands to see these kernal parameters file or files. (1 Reply)
Please clarify on below two which one is the latest Kernal version.
Also clarify me , how to break and understand, which part meant for what?
kernel-2.6.18-348.6.1.el5.i686.rpm
kernel-2.6.18-308.11.1.el5.i686.rpm
Thanks (3 Replies)
HI All,
server stopped here, we are suspecting server crash, need install new OS.
Any suggestions on this. kindly help to us.
Thanks
Rajesh (0 Replies)
Discussion started by: Rajesh_Apple
0 Replies
LEARN ABOUT SUNOS
sem_overview
SEM_OVERVIEW(7) Linux Programmer's Manual SEM_OVERVIEW(7)NAME
sem_overview - overview of POSIX semaphores
DESCRIPTION
POSIX semaphores allow processes and threads to synchronize their actions.
A semaphore is an integer whose value is never allowed to fall below zero. Two operations can be performed on semaphores: increment the
semaphore value by one (sem_post(3)); and decrement the semaphore value by one (sem_wait(3)). If the value of a semaphore is currently
zero, then a sem_wait(3) operation will block until the value becomes greater than zero.
POSIX semaphores come in two forms: named semaphores and unnamed semaphores.
Named semaphores
A named semaphore is identified by a name of the form /somename; that is, a null-terminated string of up to NAME_MAX-4 (i.e., 251)
characters consisting of an initial slash, followed by one or more characters, none of which are slashes. Two processes can operate
on the same named semaphore by passing the same name to sem_open(3).
The sem_open(3) function creates a new named semaphore or opens an existing named semaphore. After the semaphore has been opened,
it can be operated on using sem_post(3) and sem_wait(3). When a process has finished using the semaphore, it can use sem_close(3)
to close the semaphore. When all processes have finished using the semaphore, it can be removed from the system using
sem_unlink(3).
Unnamed semaphores (memory-based semaphores)
An unnamed semaphore does not have a name. Instead the semaphore is placed in a region of memory that is shared between multiple
threads (a thread-shared semaphore) or processes (a process-shared semaphore). A thread-shared semaphore is placed in an area of
memory shared between the threads of a process, for example, a global variable. A process-shared semaphore must be placed in a
shared memory region (e.g., a System V shared memory segment created using shmget(2), or a POSIX shared memory object built created
using shm_open(3)).
Before being used, an unnamed semaphore must be initialized using sem_init(3). It can then be operated on using sem_post(3) and
sem_wait(3). When the semaphore is no longer required, and before the memory in which it is located is deallocated, the semaphore
should be destroyed using sem_destroy(3).
The remainder of this section describes some specific details of the Linux implementation of POSIX semaphores.
Versions
Prior to kernel 2.6, Linux supported only unnamed, thread-shared semaphores. On a system with Linux 2.6 and a glibc that provides the NPTL
threading implementation, a complete implementation of POSIX semaphores is provided.
Persistence
POSIX named semaphores have kernel persistence: if not removed by sem_unlink(3), a semaphore will exist until the system is shut down.
Linking
Programs using the POSIX semaphores API must be compiled with cc -pthread to link against the real-time library, librt.
Accessing named semaphores via the filesystem
On Linux, named semaphores are created in a virtual filesystem, normally mounted under /dev/shm, with names of the form sem.somename.
(This is the reason that semaphore names are limited to NAME_MAX-4 rather than NAME_MAX characters.)
Since Linux 2.6.19, ACLs can be placed on files under this directory, to control object permissions on a per-user and per-group basis.
NOTES
System V semaphores (semget(2), semop(2), etc.) are an older semaphore API. POSIX semaphores provide a simpler, and better designed inter-
face than System V semaphores; on the other hand POSIX semaphores are less widely available (especially on older systems) than System V
semaphores.
EXAMPLE
An example of the use of various POSIX semaphore functions is shown in sem_wait(3).
SEE ALSO sem_close(3), sem_destroy(3), sem_getvalue(3), sem_init(3), sem_open(3), sem_post(3), sem_unlink(3), sem_wait(3), pthreads(7), shm_over-
view(7)COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the
latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
Linux 2017-05-03 SEM_OVERVIEW(7)