Is it really necessary to re-install the dialog instances?

Question

Hi,
We are upgrading from NW04 (WAS 6.40) to NW04s (WAS 7.00) ABAP SR2  only  on Windows 2003 with Oracle 9i. There is no JAVA stack in our environment and we don't need it.
In production system we have five separate dialog instances on five different physcial machines. All these application servers runnon Windows 2003 as well.
Reading through the NW04s upgrade guide "SAP NetWeaver 2004s
Application Server ABAP" dated 28th November 2006,
<u><b>section 6.26</b></u> states we have to "install the new dialog instance on top of the old dialog instance".
In the past upgrades eg. upgrade to NW04, we did not have to use SAPINST to re-install the dialog instance. Instead, the official NW04 (WAS6.40) upgrade guide just instructs us to amend instance profile parameters and copy the new version of kernel binaries either manually or using sapcpe.
I want to avoid doing this re-installation work for the five dialog insatnces. Because I want to reduce the production outage period.
Question all the upgrade experts
1) Does any one have experience that indicates I should follow the SAP documentation to un-install 6.40 instance and then re-install at 7.00 level again?
2) Also, what is the technical reason to uninstall and re-install?
The full section 6.26 section paragraph is pasted here.
<i><b>6.26 Upgrading or Installing Dialog Instances
After the upgrade of the central instance, you need to upgrade the dialog instance to the new release.
To do this, you install the new dialog instance on top of the old dialog instance using the tool SAPinst.
You can now also install additional dialog instances, if necessary.
Procedure
Proceed as described in the document Installation Guide &#8210; <SAP NetWeaver / SAP solution> <Technology> on
<Operating System>: <Database>.
Caution
If you upgrade a dialog instance, make sure to use the same instance number as on the source release.</b></i>

Answer 1

Hi Matt,
Thanks for your detailed response. Our system is very much heavy batch processing oriented. Therefore our management does not want to hand over the production system until all dialog instances are ready at the new version.
It would be great if the upgrade process is quick as you pointed out.
Can you show me where this  "upgrade dialog instance" option  in V7 SAPINST? FYI. I should be able to start sapinst over the next few days to look for this upgrade option.
However, I just got a response from ASIA-PACIFIC OSS that says I have to un-install and re-install  the existing dialog instance. Their response is as follows :
<i><b>The dialog instance does not need to be upgraded since in the dialog
instance, no database exists but only the kernel files and some
profiles exist. After the upgrade, you should re-install the dialog
instance since in the central instance, the kernel release has been
changed to 700 due to the upgrade. But in the old dialog instance,
it should still have the old release kernel files and profiles.
Thus, by using reinstallation, the new release kernel files will be
installed in the dialog instance.
As to the procedure, you should uninstall the old instance firstly since during the installation, the files will be put to the same path of the
old instance.We recommend you to backup the old dialog instance files
before the installation.Sorry there is no related note but you can refer to the upgrade and installation guides.</b></i>
Thanks for your input and assistance.
Benny Kwan
National Australia Bank