03-28-2012
There is a substantial Wikipedia on this subject (and links to more articles):
Paging - Wikipedia, the free encyclopedia
Quote:
If I have 8Gb RAM and 8Gb swap and an application requests 20Gb will it run out of memory?
No: The request will be refused.
Btw. The old rule that you must have at least as much swap as you have memory does not apply to modern unix.
Many modern unix systems can be configured to use part of memory for swap. This allows the O/S to defragment main memory quickly and quietly.
If you have Oracle, buy enough memory so that it should never swap and be sure that you understand how to size the SGA and PGA and how to measure these sizes using Oracle itself. It is very common to missize the SGA by a factor of 8 or even 16.
Last edited by methyl; 03-28-2012 at 02:20 PM..
7 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hi
How can I determine if swapping is occuring on a server.
Thanks,
Leo (2 Replies)
Discussion started by: leo
2 Replies
2. AIX
Hi everyone,
I need to write some AIX scripts (ksh?), kind of fast so I'm looking for somewhere to get a crash course in it. Are there any AIX Specific Scripting resource sites that anyone can recommend, really not getting a whole lot from google.
Thanks in advance,
Darren (3 Replies)
Discussion started by: dbridle
3 Replies
3. SuSE
Hello!
Why does my SuSE GNU/Linux machine swap?
I have a Gig of ram, currently 14MBs of free RAM, 724MB - buffers and caches...
That is 685MB of cached RAM, then kernel really should'nt have to swap, It should release cached memory in my thinkin...
It has only swaped 3MB's but still,... (3 Replies)
Discussion started by: Esaia
3 Replies
4. UNIX for Advanced & Expert Users
Hi friends,
I urgently need to know if there is any tool called source reader in C or Unix or Linux......
If so ..plz let me know the details.I am running out of time..... (0 Replies)
Discussion started by: vijaya2006
0 Replies
5. UNIX for Dummies Questions & Answers
Is there a good book or something on practical programming in X11? I have the O'Reilly X window system book set. They don't seem to cover the nuances very well (at least for me). So far the only thing I find on the web is the text from these books.
Specifically, I'm looking for optimization... (2 Replies)
Discussion started by: willil
2 Replies
6. Solaris
Experts,
I know when I use id it shows only the primary group information for the given user, and that info comes from passwd file. When I use groups it shows all groups user are member of, however from where come information given by groups command?
grep fmtt3990 /etc/passwd... (6 Replies)
Discussion started by: fmattos
6 Replies
7. Solaris
Hi Guys
I am using SPARC-T4 (chipid 0, clock 2998 MHz), SunOS 5.10 Generic_150400-38 sun4v.
How do I see if the server was doing some swapping like yesterday?
I had a java application error with java.lang.OutOfMemoryError, now I want to check if the server was not doing some swapping at... (4 Replies)
Discussion started by: Phuti
4 Replies
LEARN ABOUT HPUX
remote_nfs_swap
remote_nfs_swap(5) File Formats Manual remote_nfs_swap(5)
NAME
remote_nfs_swap - enable swapping across NFS
VALUES
Default
Allowed values
DESCRIPTION
This tunable controls adding a NFS filesystem for use as swap. If is set to only local filesystems and devices can be used for swap. If
it is set to both local and networked file systems can be used for swap.
Historically, this tunable was used in NFS clusters that are no longer supported, but this capability has not yet been removed.
Who Is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect on the next boot.
When Should the Tunable Be Turned On?
Almost never. As previously mentioned, this tunable was designed for systems which are not in use today. Only systems with extremely
robust NFS capabilities should even consider using NFS for swap.
What Are the Side Effects of Turning the Tunable On?
If the value is set to and a NFS partition is added as swap, then some kernel memory will be set aside for NFS transactions to the swap
file system. The kernel will then use the NFS swap partition just the same as a local file system. If the NFS capabilities of the system
are not robust, this could lead to extremely long swap times (both swap in and swap out), and possibly a loss of memory because all the
reserved memory and more could be used by NFS (just when memory pressure is high) causing the need for swap.
When Should the Tunable Be Turned Off?
Unless you are positive that the NFS system can handle the load of being used as swap, and does not have a local file system or disk drive
to spare, this tunable should be set to
What Are the Side Effects of Turning the Tunable Off?
Any previously defined NFS swap filesystems will no longer be allowed. Kernel memory will not be reserved for NFS transactions due to
swap.
What Other Tunables Should Be Changed at the Same Time?
None.
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 remote_nfs_swap(5)