When planning your upgrade strategy, note that you need to follow different upgrade paths depending on the initial situation. We differentiate between a Plug-In upgrade and a multi-level upgrade:

• A Plug-In upgrade describes an upgrade to the next R/3 Plug-In version without a corresponding update of the R/3 release (for example, PI 99 for R/3 4.5B to PI 2000.1 for R/3 4.5B). It is estimated that this upgrade takes less than four hours (usually ca. one hour).
• A multi-level upgrade is an upgrade of the R/3 system while keeping the current R/3 Plug-In release. After an R/3 upgrade from 4.0b to 4.5B has been carried out, for example, an exchange upgrade from PI 99/4.0b to PI 99/4.5B must take place.

1. Plug-In upgrades of R/3 Plug-Ins are only supported until the subsequent release (figure 1). The sole exception to this is the upgrade of B2B-PRO-PI after PI 2000.1.
2. Customers who are already productively using Plug-Ins (for example, APO-CIF für SAP APO 1.1) must first install an R/3 Plug-In release by implementing a Plug-In upgrade. The customer can carry out a multi-level upgrade to the next R/3 Plug-In release within this release.
3. Two steps are necessary between non-modifying and modifying R/3 Plug-In versions: a Plug-In upgrade from a non-modifying to a modifying version must be carried out, and then a multi-level upgrade within the modified cversion can be carried out. Multi-level upgrades are only possible within the one version.
4. You can change from a non-modifying to a modifying R/3 Plug-In version at any time. From a technical viewpoint, the modifying version (PI) is simply installed over the existing non-modifying version (PI-A). It is not possible to switch from a complete delivery to a light delivery.

The following graphic shows the upgrade paths of the individual R/3 Plug-In releases. A release cannot be skipped. "Single Plug-In" refers to all plug-ins shipped prior to R/3 Plug-In.

The next figure shows the upgrade paths for existing single Plug-Ins (before release PI 99, and after R/3 Plug-In, or from release PI (-A)99 after PI(-A) 2000.1). The letter ‘A’ (for example NDI-A/30h) in the release name indicates that it is part of a non-modifying Plug-In.