RE: Freeable memory

From: Diego Cutrone <dcutrone_at_afip.gov.ar>
Date: Thu, 17 Jan 2002 10:32:16 -0800
Message-ID: <F001.003F2F83.20020117100449@fatcity.com>

Hi Michael:

      Why don't you use this Steve Adams' script to check the fragmentation of your shared pool, it may be badly
fragmented and this problem could generate a lot of pressure at the shared pool latch.
And this situation can also generate contention at a lower level latch (like the library cache latch).
Make sure the session has been up and running for some time before running it and don't execute any
shared pool flush before running it, or your data would be misleading.

       Here's the script, or you can dowload it from IXORA site. www.ixora.com.au

---

---

---

---
--

• Script: shared_pool_free_lists.sql
• Purpose: to check the length of the shared pool free lists
• For: 8.0 and higher
  --
  
• Copyright: (c) 2000 Ixora Pty Ltd
• Author: Steve Adams
  --
  
• Warning: This script queries x$ksmsp which causes it to take the
• shared pool latch for a fairly long time.
• Think twice before running this script on a large system
• with potential shared pool problems -- you may make it worse.
  --
  

  ---

  
  ---
  @save_sqlplus_settings

select
  decode(sign(ksmchsiz - 80), -1, 0, trunc(1/log(ksmchsiz - 15, 2)) - 5)     bucket,
  sum(ksmchsiz) free_space,
  count(*) free_chunks,
  trunc(avg(ksmchsiz)) average_size,
  max(ksmchsiz) biggest
from
  sys.x_$ksmsp
where
  inst_id = userenv('Instance') and
  ksmchcls = 'free'
group by
  decode(sign(ksmchsiz - 80), -1, 0, trunc(1/log(ksmchsiz - 15, 2)) - 5) /

@restore_sqlplus_settings

---

---

HTH
Diego Cutrone

• Original Message ----- To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Sent: Wednesday, January 16, 2002 7:10 PM

> All,
>   In trying to solve some Library Cache latch contention issues, I've been
> stumped on the following issues:
>
>   1) Do freeable chunks get coalesced during an ALTER SYSTEM FLUSH
> SHARED_POOL.
>   2) If freeable chunks are freed when a session disconnects, is there a

way

> to determine chunks per session? The idea here is better memory management
> through better session management.
>
>   I've aleviated the majority of latch contention by altering the
> _kgl_latch_count parameter, but haven't addressed what I think is the root
> cause: an oversized shared pool. I've found scripts that show the amount

of
> memory occupied by the sql area and library cache, and most if the memory is

> in freeable chunks. Before downsizing the shared pool, I'd like to have a
> better understanding of how these chunks are managed.
>
> Regards,
>   Mike G
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Michael Ghelli
>   INET: mghelli_at_precise.com
>
> Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
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--

Please see the official ORACLE-L FAQ: http://www.orafaq.com
--

Author: Diego Cutrone
  INET: dcutrone_at_afip.gov.ar

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists


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to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Received on Thu Jan 17 2002 - 12:32:16 CST