S/4HANA Upgrade: Lessons Learned

Upgrading SAP S/4HANA to release 2023 (particularly when moving from several releases prior) is a complex process that requires careful planning, resource allocation, and thorough testing. Based on our experience, here are some key lessons learned to ensure a successful upgrade.

Planning

Mock Cut-Over & Upgrade: Schedule a mock cut-over and mock upgrade in the target environment for NP1. This helps refine timing, uncover potential issues, and validate the upgrade process.
Testing in Mock Environment: Perform rigorous testing of RF transaction codes and ME activities, including product costing, in the mock environment with the latest data to identify potential upgrade challenges.

Resourcing

Ensure that in addition to SAP Basis, ABAP, and functional teams, you also involve:

EDI specialists to handle integrations.
Security experts to address role adjustments.
Infrastructure teams to prepare for system and hardware impacts.

Pre-Upgrade Activities

ATC Checks: Run ATC (ABAP Test Cockpit) custom code checks, specific to the target release, at least two months before implementation. Review all recommendations carefully and add pseudo-comments if needed.
Deleted Objects: SAP may remove objects considered obsolete, including custom objects within the SAP namespace. Before the upgrade:

Identify all custom objects in TADIR where the original system is SAP.
Modify the original system value to prevent unintended deletions.
This is particularly crucial for third-party add-ons with custom namespaces.

During the Upgrade

XLCA Step Execution: If upgrading from older releases, manually execute the XLCA step in each environment before starting the upgrade. This prevents transaction posting errors. Reference SAP Note 2918366 for guidance (link).
Security & Role Changes: SAP modifies roles, including custom ones, during the upgrade. Ensure significant security team involvement to:

Review changes.
Adjust roles as necessary.
Reactivate custom roles to maintain system integrity.

SDM Monitoring: After the Software Update Manager (SUM) phase completes:

Check SDM_MON to confirm all tasks have been successfully executed.
If pending tasks exist, ensure the SDM process is scheduled to run and monitor its completion.

Testing Considerations

Month-End Close in UAT: Require all business units to conduct a full month-end close during User Acceptance Testing (UAT), including product costing validation.
RF Transactions Testing: Confirm that all RF (Radio Frequency) transactions function properly post-upgrade to avoid disruptions in warehouse and logistics operations.

Cut-Over Planning

Increase Disk Space: Ensure additional disk space is available on the production server to accommodate the database logs generated during the upgrade.
Database Log Handling: Consider turning off database incremental logs, as the upgrade process results in massive data updates that can quickly consume available storage.

Final Thoughts

The upgrade from SAP S/4HANA 1909 to 2023 is a major undertaking that requires detailed planning, proactive issue resolution, and a dedicated team across multiple functions. By applying these lessons learned, organizations can reduce risk, minimize downtime, and ensure a smoother transition to the latest S/4HANA release.