Re: SEQONLY(*YES nnn) recommendations on how big a block?

[Charles Wilt <charles.wilt@xxxxxxxxx>]

pretty sure those values are still valid...

On your application that writes 20M records to a journaled table, are you
using commitment control?

If not, re-read the book. :)  Note that the Journal Caching PPRQ mentioned
is now a LICPGM..
5770SS1    42      HA Journal Performance

Rob has posted many times in the past that he got more improvement out of
the journal caching than going to all SSDs.

Charles


On Fri, Jul 14, 2017 at 12:40 PM, Dan <dan27649@xxxxxxxxx> wrote:

> In the "General performance considerations" chapter of the redbook Striving
> for Optimal Journal Performance on DB2 Universal Database for iSeries
> (SG24-6286-00), it has the following recommendation:
>
> "Specify Sequential Only on OVRDBF
> Where possible, use the CL command OVRDBF to specify sequential-only
> processing when adding rows to your database tables. Also, consider using
> separate open data paths (ODPs) and open these for output when adding large
> amounts of rows to your database tables.
> Also, specify the NBRRCDS parameter with a value as close to
> 128KB/row-width as possible to maximize memory buffer utilization."
>
> I have tested this, especially since we turned on journaling and
> performance on this one application that writes 20M records to a table, and
> found a signficant boost in performance. But I note that this redbook was
> written 15 years ago and mentions in the edition notes that "This edition
> applies to Version 5 Release 1 of OS/400".  Can anyone advise whether this
> particular recommendation, specifically WRT the 128KB/row-width, still
> applies today?  (We're on Power 8, v7r1.)  If I go with a bigger block than
> 128KB, at what point do I need to be concerned with resource contention?
>
> - Dan
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