How to execute S/4HANA system upgrade using Zero Downtime Option of SUM – PoC customer case

In this blog, I would be sharing the details about the SAP S/4HANA upgrade from 1809 to 1909 using ZDO of SUM tools and lessons learned as part of Proof of Concept – PoC

Introduction

There are many reasons why customer plans to upgrade the SAP S/4HANA system.

For example

• Get business benefits through the  latest available features, functionalities, and innovations in SAP S/4HANA​
• Stay within SAP Standard Maintenance ​
• Take advantage of the lasted available bug fixes and performance improvements

Check out Jocelyns blog post Upgrading SAP S/4HANA AnyPremise – How, Why, and Best Practices guide now available!.

However, an upgrade of the SAP S/4HANA system requires a downtime. Not every customer likes can afford a lengthy downtime of their SAP S/4HANA system due to increased business demands.

For this reason, SAP offers various approaches and options to minimize the impact to their critical business operations to reduce the downtime of their SAP systems for such maintenance activities.

Software Upgrade Manager (SUM) is one of the important tools used for upgrading any S/4HANA system. By the time I write this blog SUM got the following option for upgrades.

1. Standard
2. nZDM (near Zero Downtime)
3. ZDO (Zero Downtime Option by Jens Fieger )

In this blog, I will focus on ZDO only. If you are not familiar with how to plan a ZDO upgrade please go through my blog – Zero Downtime Option (ZDO) of SUM – SAP Upgrade Project Planning

Please check the following SAP Note before you start planning the S/4HANA upgrade using ZDO to understand the availability, applicability and the constraints.

2707731 – Prerequisites and restrictions of Zero Downtime Option of SUM for SAP S/4HANA.

Lessons learned from ZDO Proof of Concept Scope

Zero Downtime Option (ZDO) POC for SAP S/4HANA release upgrade from S/4HANA 1809 to 1909 approximately 4TB SAP HANA DB size. After the scope confirmation customer registered for the ZDO workshop and to execute the ZDO POC. The registration process described in SAP Note 2707731  is mandatory since the ZDO is available on a pilot basis. After successful registration, the SAP ZDO product management will provide you with the magical key to enable the ZDO.

Following is the execution rundown of critical ZDO phases with runtimes

As a result of the POC, the ZDO option took just 4 minutes of app servers to restart time to move from SAP S/4HANA 1809 over to the target release SAP S/4HANA 1909.

Like any other upgrade, ZDO of SUM will go through all the initial phases of the regular SUM tool. For example, Extraction, Configuration, Checks, Shadow Instance, Repository Lock, and SPDD on Shadow. Logically technical ZDO phase starts from the middle of the Preprocessing phase.

ZDO Impact analysis:- 

A detailed impact analysis was performed to identify the read-only table and cloned tables with the highest change rate for the duration of bridge time. Identified critical restrictions were addressed with the support of the SAP development team in the form of SAP notes.

Overall, no significant tables were identified under read-only tables. Refer for more details about impact analysis Impact Analysis as part of Software Update Manager 2.0

ZDO User Rollover to Bridge:-

After all the technical preprocessing activities, the users on the sandbox system are rolled over successfully without any interruption to their regular transactions. However, the user rollover phase took around 34 mins due to known issues HANA DB user store. The user store should be shared globally. However, if the user store is located on a local drive, it’s important to consider the steps outlined in the central SUM SAP Note for SAP HANA. For the latest SUM 2.0 SP09, it’s SAP Note 2935077.

ZDO Uptime on the Bridge:-

Users were on the bridge instance for about 27 hours without any interruption to their regular business transactions. While the upgrade is running, in the background, SUM upgrade phases are executed for 15 hours.

App server Restart by SUM:-

After 15 hours of upgrade phases execution, the SUM informed the basis team that upgrade downtime phases are completed and ready for the restart of the application server to move to the target release. Since the completion popup arrived at midnight. The application server restart executed during the working hours.

SUM tool took 4 mins to restart the two application servers. This is the only time where the system was not available for any use.

Note:- the above-mentioned numbers are SUM execution runtimes. No dialog times(inputs, SPDD, SPAU, issues resolution, ramp down, ramp up ect…) are not counted.

Post Processing:-

The new SUM tool came up with the option to continue  the SUM post work with business validation. The same has flowed in the POC. This is a generic SUM capability introduced very recently.

ZDO Specific SUM screens :

Note: Following screens are based on the SUM 2.0 SP8 PL 03. You will only find ZDO specific screen that impacts ZDO processes. You can find generic SUM screens in many SAP blogs.

Generic Stack XML screen

ZDO option is available only as a Pilot at the time of this blog. Please refer to SAP Note  2707731  and ZDO Blog for the latest information. To enable this option in the SUM tool you need to register, and magical key provided by the ZDO product manager after checking the feasibility.

 You will start seeing the ZDO option on the SUM tool header as a select upgrade method for the current upgrade.

If there are any SLT triggers on the current system ZDO of the SUM tool request the RFC connection to the central system to handle the SLT triggers as part of processes.

Please check blog SAP blogs for more details on SLT trigger handling with Software Update Manager 2.0

Silent Data Migration is a new concept introduced starting from S/4HANA 1909 and higher and this does not depend on the SUM tool rather it is triggered depending on the target release.

For more details please check the blogs  Silent Data Migration and Monitoring Silent Data Migration

Shadow instance number: Once all the shadow instance phases are completed SUM tool uses the Shadow instance number for running the downtime relevant phases while the users are transacting from the bridge instance.

Impact analysis: When using the ZDO users might see certain impacts on tables and additional database space when they are on the bridge instance. Using the impact analysis, you can identify the potential impacts with respect to the production cycle in the POC itself. This will help the customer to decide whether to move on with ZDO or not.

For more details please check SAP blog Impact Analysis

User Roll-Over to Bridge system – 1^st screen

Very important  ZDO phase. You will see the screen when all the ZDO preparatory steps are completed and the SUM tool is ready to enter the upgrade downtime and roll users to the bridge phase.

When you click next on this SUM screen, all the users will be rolled over to bridge instance without any disruption and seamlessly.

User Roll-Over to Bridge system – 2^nd screen

Once all the sessions are successfully connected to the bridge instance SUM stops at the screen to provide confirmation. You will not see this screen in case if you have any issues with any session.

Here onwards all the users will logically be connected to the bridge instance and continue to execute the regular transaction from the bridge instance. Underneath SUM will continue and execute upgrade phases.

User Roll-Back to Original – 1^st screen

Once all the downtime upgrade phases are completed SUM will stop at this screen to let you know that all the upgrade downtime phases are completed and ready for the app server restart.

In the production cutover, you will continue to be on the same screen till you reach the planned downtime usually Friday night. On a cutover day, first, you continue with Ramp down and click next on SUM tool. SUM will restart the application serves.

User Roll-Back to Original – 2^nd screen

You will see this screen after all the application servers are restarted along with few other SUM phases.

After the restart, you will be on the target release and you should be able to continue with POST steps like SPAU etc..

Hold the SUM till you complete Post work

This is a new feature recently introduced in the SUM tool to parallelize the post-processing time of the SUM tool. In this phase, you can pause the SUM execution and continue with post-work basis work (exp SPAU, Post transport import, configuration, etc..). After you are done with post-work, you can execute the SUM post-processing phase while business validation is going on.

Well, this is the SUM completion screen. However please note that the upgrade is not completed.

You need to complete the new S/4HANA upgrade feature called Silent Data Migration (SDM ). The SDM is automatically triggered by the SUM tool and it will wait for you to execute BTCTRANS2 to release its background job SAP_SDM_EXECUTOR_ONLINE_MIGR.

For more details please check my SAP blogs  Silent Data Migration and Monitoring Silent Data Migration

Let me repeat this one more time, SDM is independent of the SUM tool options(nZDM, ZDO)  rather it depends on the target release of S/4HANA. They are executed after the upgrade and parallel to transaction usage on the target system.

In this POC following list of SDM classes executed after the upgrade using ZDO.

Summary

Isn’t it really interesting to see a SUM tool with no downtime!! Or an upgrade to target release with a downtime of an application server restart!!

For more details:

• Replay of SAP TechEd 2019: CAA301 – Leveraging Zero-Downtime Maintenance for SAP S/4HANA
• Replay of SAP TechEd 2018: CNA306 – Get Your SAP S/4HANA Ready for Running a Zero-Downtime Update Project
• SAP Notes
  2707731 – Prerequisites and restrictions of Zero Downtime Option of SUM for SAP S/4HANA
  2163060 – “Prerequisites and Restrictions of Zero Downtime Option of SUM” to get all requested info.
  2471883 – SUM Impact Analysis for ZDO

Blogs:
Leveraging Zero Downtime Option of SUM for SAP S/4HANA update/upgrades

Zero Downtime Option (ZDO) of SUM – SAP Upgrade Project Planning

Impact Analysis of Software Update Manager

Zero Downtime Option of Software Update Manager

Roadmap Viewer SAP S/4HANA Upgrade and Product Integration Roadmap

Silent Data Migration for S/4HANA 1909 upgrade/conversion

• Silent Data Migration for S/4HANA 1909 Upgrade/Conversion
• Monitoring Silent Data Migration (SDM_MON) – S/4HANA 1909 upgrade/conversion

Parishudh

IT Planning & Maintenance Optimization
Center of Expertise – Customer Success – Intelligent Delivery Group
SAP America Inc.