Command to fresh the memory ! Post: 302370270

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Operating Systems AIX Command to fresh the memory ! Post 302370270 by zxmaus on Wednesday 11th of November 2009 02:12:46 AM

11-11-2009

Moderator

First of all - what you describe is called forking and it should not happen if you have sufficient memory + pagingspace in your box and lru_file_repage is switched off. If it happens frequently, you very likely have insufficient memory in your box or some memory leaks.
Please check your avm value (what is shown in 4k pages!!) with the vmstat command - a healthy box is somewhere around 80% of physical memory. If you're dramatically exceeding it, you simply need to add physical memory or reduce the consumtion.
Check with vmo command the value of lru_file_repage - if its set to 0, than your system rarely uses pagingspace (as long as you have enough physical memory) and your system should not fork at all.
As far as I know, the only fast and reliable way apart from killing the top memory consuming processes (what is sometimes not possible because it would require to start a new process what's usually not possible when your box is really forking/inresponsive) to refresh memory is to reboot the box.
If it's possible that you're out of memory because i.e. a crashed database did not free up its shared memory, you can give it a try using ipcrm on the misallocated shared memory segments - but be careful that you don't do it on shared memory actually in use. And as stated before - this only works if you have enough free memory to start a new process. So you need to give it again and again a try until it works.
Hope that helps,
kind regards
zxmaus

zxmaus

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shmget

shmget(2)							System Calls Manual							 shmget(2)

Name
       shmget - get shared memory segment

Syntax
       #include <sys/types.h>
       #include <sys/ipc.h>
       #include <sys/shm.h>

       int shmget (key, size, shmflg)
       key_t key;
       int size, shmflg;

Description
       The system call returns the shared memory identifier associated with key.

       A  shared  memory  identifier and associated data structure and shared memory segment of size size bytes are created for key, if one of the
       following is true:

	    The key is equal to IPC_PRIVATE.  For further information, see

	    The key does not already have a shared memory identifier associated with it, and (shmflg & IPC_CREAT ) is true.

       Upon creation, the data structure associated with the new shared memory identifier is initialized as follows:

	    The and are set equal to the effective user ID and effective group ID of the calling process.

	    The low-order nine bits of are set equal to the low-order nine bits of shmflg.  The is set equal to the value of size.

	    The and are set equal to zero (0).	The shm_ctime is set equal to the current time.

Return Values
       Upon successful completion, a non-negative integer, namely, a shared memory identifier is returned.  Otherwise, a value of -1  is  returned
       and errno is set to indicated the error.

Diagnostics
       The system call fails if any of the following is true:

       [EINVAL]       The size is less than the system-imposed minimum or greater than the system-imposed maximum.

       [EACCES]       A  shared  memory  identifier  exists for key, but operations permission, as specified by the low-order nine bits of shmflg,
		      would not be granted.  For further information, see

       [EINVAL]       A shared memory identifier exists for key, but the size of the segment associated with it is less than size and size is  not
		      equal to zero.

       [ENOENT]       A shared memory identifier does not exist for key, and (shmflg & IPC_CREAT ) is false.

       [ENOSPC]       A  shared  memory  identifier  is to be created, but the system-imposed limit on the maximum number of allowed shared memory
		      identifiers would be exceeded.

       [ENOMEM]       A shared memory identifier and the associated shared memory segment are to be created, but the amount of available  physical
		      memory is not sufficient to fill the request.

       [EEXIST]       A shared memory identifier exists for key, but ((shmflg & IPC_CREAT ) and (shmflg & IPC_EXCL )) is true.

See Also
       shmctl(2), shmop(2), ftok(3)

																	 shmget(2)