ADSM-L

Re: cash hit percentage questions

2003-01-02 08:55:14
Subject: Re: cash hit percentage questions
From: Scott Walters <scott_walters AT MACKTRUCKS DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 2 Jan 2003 08:54:25 -0500
Lee, Gary D. wrote:

TSM v4.2.1, sun 3500, solaris 2.8, 2gb memory, 288gb disk.


TSM 5.1 solaris 2.8 8gb mem


Currently have a database of approximately 6.5gb at 77% utilization.  Dbbufsize 
is currently set at 192mb.  Cash hit starts out very good at 99-99.5% but 
creeps downward throughout a weeks run to around 97%.


dbbufsize 2G


I have looked in the admin guide, and they recommend a cash hit ratio of over 
98%.  However, no matter what I try, I can never seem to hit it.


I had the exact same issue.  it seem like the algorithm to determine
cache hit ratio gets skewed over time, because of the various db
intensive activities that can occur over time.

we trend our db cache hit % every five minutes and saw this 'slow leak'.
 i called support and they recommended clearing the stats.  we now
clear the cache hit ratio every 24 hours and we have been staying above
98%.  now we have identified the creation of offsite tapes drags the
cache hit down, which is OK.  the rest of the day, the cache hit % is fine.

muncie, IN is cool ;)


--
Scott Walters
Packet Pusher - "The world speaks IP"

Mack Trucks, WHQ        http://www.MackTrucks.com
2100 Mack Boulevard     Ph: 610.709.3728
Allentown, PA 18103     Fx: 610.709.2809

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