Gary,

You need to consider what's running on the system.  In general, TSM
maintenance activities should have a high hit ratio, but new incoming
files will lower the ratio.  That's because by definition, a "new" file
does not have a database entry and therefore MUST miss the cache.

Our system runs maintenance weekly and we reset the statistics just before
it starts.  All through the day while maintenance is running, the hit
ratio is 99+ percent.  After a week of backups but no maintenance, the
ratio is about 96-97 percent.  Just the nature of the beast.

I run a DB buffer pool of 128 MB on a 27 GB DB that's about 90% utilized.

Tab Trepagnier
TSM Administrator
Laitram Corporation








"Lee, Gary D." <GLEE AT BSU DOT EDU>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
12/31/2002 07:42 AM
Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        cash hit percentage questions


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

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%.

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.

Any suggestions welcome.


Gary Lee
Senior Operating Systems Analyst
Ball State University
phone 765-285-1310