paging and swapping
DBAsupport.com Forums - Powered by vBulletin
Results 1 to 6 of 6

Thread: paging and swapping

Hybrid View

  1. #1
    Join Date
    Jan 2000
    Location
    san jose
    Posts
    149

    Post

    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.

  2. #2
    Join Date
    Mar 2000
    Location
    Chennai.Tamilnadu.India.
    Posts
    658

    A Step forward

    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
    Attitude:Attack every problem with enthusiasam ...as if your survival depends upon it

  3. #3
    Join Date
    Oct 2000
    Location
    Saskatoon, SK, Canada
    Posts
    3,925
    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
    Thanx
    Sam



    Life is a journey, not a destination!


  4. #4
    Join Date
    Mar 2000
    Location
    Chennai.Tamilnadu.India.
    Posts
    658

    More on Paging and swaping

    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
    Attitude:Attack every problem with enthusiasam ...as if your survival depends upon it

  5. #5
    Join Date
    Feb 2001
    Location
    Kolkata- India
    Posts
    356

    Smile

    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
    There Nothing You cannot Do, The problem is HOW.

  6. #6
    Join Date
    Oct 2000
    Location
    Saskatoon, SK, Canada
    Posts
    3,925
    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
    Thanx
    Sam



    Life is a journey, not a destination!


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  



Click Here to Expand Forum to Full Width