Re: Why separate pools?

[Vernon Hamberg <vhamberg@xxxxxxxxxxx>]

I stronlgy recommend that you set all shared pools to *CALC. This is expert 
cache, and it affects the I/O block size for transferring data from DASD. 
*FIXED forces this size to 4K (and maybe 16K for SQL indexes, or something 
like that), but it is possible to have a block size as large as 128K. 
Expert cache uses a sliding window (about 4 minutes, I think) for measuring 
disk I/O in regard to data files. The database engine reports its I/Os to 
expert cache, which changes the block size, depending on whether access to 
data is completely sequential (large block size, since everything is 
contiguous on disk), to completely random access, where records are 
accessed by key and are not located close together on disk.

There can be tremendous gains in I/O - the actual time to bring in a block 
of any size is essentially the same, so the more you can transfer in a 
request the better.

You can see some of these numbers in WRKDSKSTS. There are 3 columns that 
report request size - the one in the middle is average size for both reads 
and writes. To the right are separate columns for each operation.

HTH
Vern

At 12:43 PM 11/23/2004, you wrote:
> Regarding wrkshrpool, F11 paging options, *FIXED vs. *CALC.
>
> Two questions:
>
> 1) If qpfradj is 2 or 3 and all the wrkshrpool paging options are *FIXED,
> doesn't the performance adjuster still continue to move ram between the
> pools with the page size remaining the same (*FIXED) across all pools (at
> 4k ? - or whatever size the pages are)?
>
> 2) If *FIXED is changed to *CALC,  isn't this what the manuals refer to as
> 'expert cache'? And doesn't that mean the expert cache only affects the
> calculation of the page size within that pool, (which indirectly affects
> the amount of ram moved in/out of the pool)?
>
>
> Regards, Jerry
>
> Gerald Kern
> IBM Certified AS/400 RPG IV Developer & RPG IV Programmer
> MIS Project Leader, Lotus Notes/Domino Administrator
> The Toledo Clinic, Inc.
> 4235 Secor Road
> Toledo, OH 43623-4299
> Phone 419-479-5535
> gkern@xxxxxxxxxxxxxxxx