First off: SAP has a long history of "recommending" certain amounts of swap. You can safely ignore these recommendations as they are complete nonsense.
If your system has some memory shortage it will start swapping. Once it does so you need the swap space and once this swap space it exhausted (or nearly exhausted) your system will start killing processes - so far, so common. But long before your swap space is exhausted you will have a severe performance degradation and you customers will be all over you to get the system back to speed - so far, so common either.
But as long as your system doesn't have a memory shortage you don't need swap space - *any* swap space! This means, while it is a god idea to have some swap space as a contingency you don't *need* it (under "normal" circumstances, which means there is indeed enough memory) at all.
SAP now recommends to configure swap space based on a simple formula: your current amount of memory times some factor (if i remember correctly it was 2). Would you increase your memory, which would make swapping even less probable their recommended amount would even increase, while there is a simple way to meet their requirements: reduce the memory of the system, which will make swapping occur more often, but SAP will recommend a smaller swap space for this (in fact now ill-tuned) system!
You see, their recommendation is simply bovine manure.
Historically the AIX kernel used an "early swap allocation" and allocated swap space for every started program, so the recommendation of SAP made - least some - sense back then. Since the days of AIX 5 (or was it with 5.1? A lot of years back for sure!) IBM changed that and now AIX uses late swap allocation. Since this change the recommendation makes no sense at all.
Regarding your error message: There is a parameter for each LV, which shows the maximum numbers of LPs that can be assigned to it. The command xoops told you will increase this maximum for the LV which holds your swap space. You can also do it using SMIT by issuing
Code:
smitty chlv
and follow the menus on screen.
I hope this helps.
bakunin
Moderator's Comments:
BTW.: i have changed the threads title to "recommended".
Hy all,
i've a little problem with the size of the swap. I've an old solaris machine, with 4Go, and swap is taking 500Mo for only 1% used at any time.
So : how can i change this size without problems ?????
(ok it may be a stupid question, but it's a real problem when you lose about 1 or 2... (3 Replies)
Hello all,
I just got a laptop with redhat linux 7.2 installed, but during the installation the installer only put 1gig of sawp space( this laptop has 1gig of RAM). To my understanding when creating swap space, the size is determine by double the RAM. Therefore my question is that how do I... (2 Replies)
I have a machine: SunOS <server> 5.9 Generic_117171-15 sun4u sparc SUNW,Sun-Fire-480R
It has these filesystems:
Filesystem size used avail capacity Mounted on
/dev/md/dsk/d0 19G 15G 3.9G 80% /
/proc 0K 0K 0K 0% /proc... (6 Replies)
few questions
a. where can I find the RAM of a server? im about to install redhat on a server (reformat). need to know because it will be my basis for swap size. i saw something line 3048MB detected upon boot. is this the memory?
b. what is the command in lunux to check the original size of... (2 Replies)
Dear All,
How to increase the swap size when physicall memory reaches 60 %. OR it can be only done after the physicall memory is full.
Rgds
Rj (8 Replies)
Hi All,
I want to know how to understand the actual swap size.
My o/p shows as below
root@ecovs1a # swap -s
total: 4546056k bytes allocated + 358856k reserved = 4904912k used, 5046688k available
root@ecovs1a # swap -l
swapfile dev swaplo blocks free
/dev/md/dsk/d31 ... (9 Replies)
Hi Experts,
Need your advise in determining the size of swap space in of the new HP-Ux server.
Server is having 32G of physical memory.
Ideally what amout of physical memory should be allocated as a swap space?
Following document from HP suggests to have minimum swap space... (2 Replies)
Hi,
the /tmp size is less whereas the size allocated to swap is quite big. how to increase the size of /tmp -
#: swap -l
swapfile dev swaplo blocks free
/dev/md/dsk/d20 85,20 8 273096 273096
#: swap -s
total: 46875128k bytes allocated + 2347188k reserved =... (2 Replies)
Discussion started by: psb74
2 Replies
LEARN ABOUT HPUX
swapon
swapon(2) System Calls Manual swapon(2)NAME
swapon() - add swap space for interleaved paging and swapping
SYNOPSIS
Remarks
The ANSI C "" construct denotes a variable length argument list whose optional and required members are given in the associated comment
DESCRIPTION
The system call makes a block device or a directory named path available to the system for paging and swapping.
priority indicates the order in which the swap space from the device or file system is used. It has a range of 0 (highest) to 10 (lowest).
Space is taken from the lower-numbered systems first.
can be used only by users who have appropriate privileges.
If path names a block device file
makes it available to the system at the specified priority for allocation for paging and swapping.
In this form, takes only two arguments: the path to the block device file, and the priority.
The device associated with path can be a device already known to the system, defined at system configuration time, or it can be a previ-
ously unspecified device.
If the device was already defined at system configuration time and also has a start and/or size defined for that swap device, these values
are used.
Otherwise, if a filesystem exists on the device, swap is added following the filesystem, or if no filesystem exists, the complete device is
used for swap.
See the appropriate system administrator's manual for information on how the size of the swap area is calculated.
If path names a directory
makes the blocks on the file system rooted at path available for paging and swapping.
The min, limit, and reserve arguments are passed and used only if the path argument names a directory.
min indicates the number of file system blocks to take from the file system when is called.
limit indicates the maximum number of file system blocks the swap system is allowed to take from the file system.
reserve indicates the number of file system blocks that are saved for file system use only.
For a pre-existing directory swap, a value of -1 for min, limit, reserve, or priority will keep the value unchanged. This can be used to
change selective values without affecting others. For example, if priority of a pre-existing directory swap needs to be changed without
affecting the values of min, limit, or reserve, one can specify the new priority value and pass -1 for other arguments.
The size for the file system blocks mentioned above is the preferred file system block size. The preferred file system block size can be
obtained by the call. The value of min, limit, or reserve is rounded up to the tunable size.
ERRORS
If fails, is set to one of the following values.
A component of the path prefix denies search permission.
One of priority, min, limit, or reserve arguments is invalid.
The device associated with
path already has swap turned on.
The device associated with
path is already in use.
The device associated with
path was specified at system configuration time to add swap at a specified location, but that location is within an
existing file system on the device.
The LIF header on the device associated with
path contains inconsistent directory data.
Unable to read the device associated with
path.
Too many symbolic links were encountered in translating the path name.
The length of the specified path name exceeds
bytes, or the length of a component of the path name exceeds bytes while is in effect.
The device associated with
path does not exist.
The system-imposed limit on the number of swap file entries has been reached.
There is is not enough available space
on the specified file system or device.
The device associated with
path was specified at system configuration time to add swap following the file system, but no file system was found.
The path argument is not a block special file or the root directory of a file system.
A component of the path is not a directory.
The device associated with
path could not be opened.
The effective user ID is not a user with appropriate privileges.
The device associated with
path is read-only.
WARNINGS
On systems running VxVM 3.5, the swap volumes to be configured for system crash dumps should be created with the usage type as during the
creation of the swap volume. Not doing so will cause a dump corruption. You could use the option of to do the same.
No means is available to stop swapping to a device.
The system allocates no less than the amount specified in min. However, to make the most efficient use of space, more than the amount
requested might be taken from the file system. The actual amount taken will not exceed the number of file system blocks indicated in
reserve.
Swapping to a file system is usually slower than swapping to a device.
Once file system blocks have been allocated for swap space, the file system can not be unmounted unless the system is rebooted.
is the replacement for is to be obsoleted at a future date.
AUTHOR
was developed by the University of California, Berkeley.
SEE ALSO swapon(1M), vxassist(1M), swapctl(2), privileges(5).
TO BE OBSOLETED swapon(2)
10-13-2011
