00561 - Journaling to separate User-ASP

00561 - Journaling to separate User-ASP

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Journaling to separate User-ASP

Hi all!

Backup and recovery V4R5 says:
Nothing new, I would say.

The Performance Capabilities Reference
pointing to a PDF:
has more to say:
From Page 65:
The impact to performance from adding journaling can be reduced by locating
the journal receiver on a separate user ASP. Doing this will generally
the seek time required to access the disk arms for journal I/O which will in

turn help reduce the impact to end user response time. It will also lessen
impact to the disk arms located on the system ASP.

When using a separate user ASP for journal receivers,
it is important to consider the number of disk actuators available in the
Customer environments with heavily used journal receivers located in a user
that consists of a single disk actuator may actually reach a limit to
because of the high usage of this single actuator. In this case, it would be

better to have multiple disk actuators available in the user ASP so that
DB2/400 journaling support can interleave journal entries over the multiple
actuators, thus reducing contention for any one single disk arm. Doing this
may result in an improvement in response time and in overall system
However, it is important to note that although adding an actuator may
a significant improvement in performance, each additional actuator added
this will improve performance to a lesser degree. Once the utilization of
actuators is low, adding more actuators will not improve performance.

Having two or more journal receivers located on the same user ASP and having
them in use at the same time may not take full advantage of the performance
gains seen by isolating a single journal receiver on the User ASP since the
seek distance on the actuator increases as the journal entries are written
to the two receivers.

As this is from the V4R5 book, the recommendation has not changed
over time.

On all production machines, we have the JrnRcvs in ASP2 with mirrored
disks, one machine with 2 pairs for one journal, the other one with
3 pairs for two journals of two instances.

Dipl.-Ing. Rudolf Wiesmayr /\ Tel: +43 - 0732 / 7070 - 1720
SAP R/3 BASIS & /\ Fax: +43 - 0732 / 7070 - 54 1720
AS/400 Professional System Administrator (IBM Certified Specialist)
Magistrat Linz, ADV/SB, Gruberstrasse 40-42, A-4041 Linz, Austria
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