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

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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