Does it make sense to reduce the total shared memory
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 and not using that much shared memory, does it make sense to shrink the amount of shared memory allocated to reduce the swap usage? I have read that setting /dev/shm does not allocate memory. But I wonder if it is still preventing non shared memory from staying in physical memory.
I am running HP-UX B.11.11.
I'm increasing a parameter for a database engine so that it uses more memory to buffer the disk drive (to speed up performance). I have over 5GB of memory not being used.
But when I try to start the DB with the increased buffer parameter I get told.
"Not... (1 Reply)
I am using the ZLIB_VERSION "1.2.3" . The memory requirement for Zlib/GZIP compression is stated as
/* The memory requirements for deflate are (in bytes):
(1 << (windowBits+2)) + (1 << (memLevel+9))
that is: 128K for windowBits=15 + 128K for memLevel = 8 (default values)
... (0 Replies)
08-18-2008 11:00 AM
Cluster computing has played a pivotal role in the way research is conducted in educational environments. Because the amount of available money and hardware varies between university researchers, often it's necessary to find a clustering solution that can work well on a small... (0 Replies)
I've been referring bash info for processes and came across a structure for a process which is defined like
typedef struct process
{
struct process *next;
char ** argv
.
.
.
}process;
What I don't understand is that in the program there's a for loop which goes like this
job... (2 Replies)
Hi,
Im working on Solaris 9 on SPARC-32 bit running on an Ultra-80, and I have to find out the following:-
1. Total Physical Memory in the system(total RAM).
2. Available Physical Memory(i.e. RAM Usage)
3. Total (Logical) Memory in the system
4. Available (Logical) Memory.
I know... (4 Replies)
I'm running the following rsync command to sync a directory between the 2 servers:
rsync -az --delete --stats /some_dir/ server_name:/some_dir
I'm getting the following output:
Number of files: 655174
Number of files transferred: 14221
Total file size: 1138531979331 bytes
Total... (0 Replies)
Can someone explain the correlation between how sar names the disk drives and how the rest of the OS names the disk drives?
sar lists my disk drives as sd0, sd1, sd2, etc.....
while format lists my disk drives as c1t0d0, c1t1d0, c1t2d0,etc...
And also why sar shows 8 disks but format... (2 Replies)
Hello.
I am new to this forum and I would like to ask for advice about low level POSIX programming.
I have to implement a POSIX compliant C shared library.
A file will have some variables and the shared library will have some functions which need those variables.
There is one special... (5 Replies)
I stumbled upon this thread and one aspect of it got me thinking. As i am building a small Linux network right now for a friend i would like to hear your opinion on this.
I'd like to respectfully disagree. I think the Linux habit of disabling root login per default is wrong (not entirely... (6 Replies)
I am using xlC (Version: 11.01.0000.0011).
While build i am using "-g" to have debug information in build.
there are many object files (>500) due to which resultant shared file (.so) will have huge size.
I can't reduce optimization level.
Is there any way or flag is present by using which i... (2 Replies)
Discussion started by: Abhi04
2 Replies
LEARN ABOUT OSX
shmdt
SHMAT(2) BSD System Calls Manual SHMAT(2)NAME
shmat, shmdt -- map/unmap shared memory
SYNOPSIS
#include <sys/shm.h>
void *
shmat(int shmid, const void *shmaddr, int shmflg);
int
shmdt(const void *shmaddr);
DESCRIPTION
shmat() maps the shared memory segment associated with the shared memory identifier shmid into the address space of the calling process. The
address at which the segment is mapped is determined by the shmaddr parameter. If it is equal to 0, the system will pick an address itself.
Otherwise, an attempt is made to map the shared memory segment at the address shmaddr specifies. If SHM_RND is set in shmflg, the system will
round the address down to a multiple of SHMLBA bytes (SHMLBA is defined in <sys/shm.h> ). A shared memory segment can be mapped read-only by
specifying the SHM_RDONLY flag in shmflg. shmdt() unmaps the shared memory segment that is currently mapped at shmaddr from the calling
process' address space. shmaddr must be a value returned by a prior shmat() call. A shared memory segment will remain existant until it is
removed by a call to shmctl(2) with the IPC_RMID command.
RETURN VALUES
shmat() returns the address at which the shared memory segment has been mapped into the calling process' address space when successful,
shmdt() returns 0 on successful completion. Otherwise, a value of -1 is returned, and the global variable errno is set to indicate the error.
ERRORS
The shmat() system call will fail if:
[EACCES] The calling process has no permission to access this shared memory segment.
[EINVAL] shmid is not a valid shared memory identifier. shmaddr specifies an illegal address.
[EMFILE] The number of shared memory segments has reached the system-wide limit.
[ENOMEM] There is not enough available data space for the calling process to map the shared memory segment.
The shmdt() system call will fail if:
[EINVAL] shmaddr is not the start address of a mapped shared memory segment.
LEGACY SYNOPSIS
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
The include files <sys/types.h> and <sys/ipc.h> are necessary for both functions.
SEE ALSO mmap(2), shmctl(2), shmget(2), compat(5)BSD August 17, 1995 BSD