paging and swapping

[bxr556]

I often heard that we can use sar to see if there are paging
or swapping is happening.

but i don't have a feeling which means bad,

if 1 atch/s mean bad, or more than 1000 atch/s means bad?

can somebody tell me more about

sar -p
atch/s
pgin/s
ppgin/s
pflt/s
vflt/s
slock/s

sar -w
swpin/s
bswin/s
swpot/s
bswot/s
pswch/s

sar -r
freemem
freeswap

sar -g
pgout/s
ppgout/s
pgfree/s
pgscan/s
%ufs_ipf

PLEASE don't just give me the meaning of those items, i can
get it from unix man, i want to know what value means bad.
what means really bad, something like that.
thanks.

[padmam]

Hi BXR, 27th May 2001 19:56 hrs chennai

This First link speaks examples in terms of values on the topic you have requested.

1)
http://uw7doc.sco.com/SM_perform/_Co...on_Demand.html

2)http://www.coresw.com/tsdocs/Updates/OracleTuningGuide.txt

3)
http://www.rdbms.org/library/unix_tuning.htm

If this doesnt interest your requirement lets wait for our team to return from weekend.

Cheers

Padmam

[sambavan]

As far as paging is concerned, page ins are more normal and page outs can occour at times. When compared to paging and swaping swaping is more expensive operation than that of paging. The paging mostly happens in memory, where as when you end up swaping then you are running out of memory and would be using the disk to store and retrive part of your contents. Which is more I/O prone too.

Always make sure that you don't get into swaping.

Sam

[padmam]

Hi, 28th May 2001 11:12 hrs chennai

Both paging and swapping needs adequate disk space to temporarily hold the memory blocks on disk.These files are I/O intensive so they have to considered when balancing I/O.

One more difference between Paging and swapping is not all the o/s supports both.Swaping is done almost by all o/s. whereas NT supports only paging.

Paging :Is used when process needs a page (Block) of memory that is no longer in Real memory but in Virtual memory.The block must be paged in from the disk and the block that it replaces has also to written back to disk.

Swapping :Is simillar to paging except that they memory space of the entire process is removed from memory.If there are too many process running swapping may increase to an unacceptable level.

Cheers

Padmam

[sudip]

I have a Solaris server (624m of physical RAM) which swaps 19M when no process ecept Unix are run. The swaping increasing to 200m when Oracle is loaded and 500M when Weblogic server is run.
I told our helpdesk guys that swapping is bad but they maintain that it is good. Can you give a link to a writeup which explains them the phenomenoin of swapping.
Thanx

[sambavan]

Here is a site that talks about paging and swaping:

http://www.netsys.com/bsdi-users/1998-05/0584.html

check chapter 3 on this lecture notes:
http://www.cs.nyu.edu/courses/spring...ass-notes.html

Hope this would help you to better undestand the problem.

Sam