Managing Product System Information 
Maintenance activities are based on product systems. Usually, you cannot install the complete product version (SAP ERP or SAP CRM, for example) on a single technical system. This would be inflexible, because reuse of installed software (of the Enterprise Portal, for example) would not be possible. Preferably, reusable product instances are installed on their own technical systems. Product system definitions describe dependencies and reuse between technical systems, so you can update the technical systems consistently and keep the solution running.
To enable reuse, only certain parts of a product version are often installed, and the installation is distributed over several technical systems. For more information, see the White Paper: SAP Solution Landscape at http://scn.sap.com/docs/DOC-29495.
Technical systems can automatically supply the System Landscape Directories (SLDs) with information about installed software, by SLD data supplier (for example, with transaction RZ70 for AS ABAP). SLDs automatically synchronize this technical system data with the LMDB in SAP Solution Manager. Based on this technical system information, you create product system information in the LMDB to define landscape data that semantically describes interdependencies between technical systems. Landscape data describes how a product version is installed on different technical systems, or which technical systems build a dual-stack. A product system is the technical systems on which selected product instances of a product version are installed. The parts of one product system must be maintained simultaneously as one unit.
For detailed descriptions of how to manage product system information in SAP Solution Manager, see the following documents:
Creating Product System Information
Technical system information is provided automatically by the System Landscape Directory (SLD), but product system descriptions must be created manually.
As of SAP Solution Manager SP09, product system information still must be created manually, but is updated automatically as soon as the information for related technical systems is updated. (Until SP08, product system information also must be updated, manually.)
Example: Product System ERP
The graphic above shows an example for an SAP ERP product system comprising two technical systems (ERP and EP1). Two product versions are installed: the stand-alone product version SAP ERP 6.0 and the dependent add-on product version Enhancement Package (EHP) 5 for SAP ERP 6.0. The product instances SAP ECC Server and Central Applications of the product versions are installed on the Application Server (AS) ABAP technical system. The Self-Services are installed on the AS Java technical system.
Product system information comprises definitions of different, logically dependent entities:
Products and Product Versions
SAP products are the applications that SAP delivers. A product groups a set of functions to solve a business need. The SAP product model (SAP software catalog) describes all SAP products. This model defines the possible product structure. A product consists of one or more product versions.
Examples of products are SAP ERP, SAP NetWeaver, and SAP Solution Manager.
A product version is a release of a product. It bundles the product instances and related software component versions available at the same time for a function. The bundle considers, for example, technical dependencies. Product versions typically have a name starting with “SAP …” and have characteristics like their application function and a maintenance period.
Example: SAP ERP 6.0 is a product version of the product SAP ERP.
Product Instances
A product instance is part of exactly one product version. A product instances bundles a set of software components that have to be installed as a unit. The individual software components cannot be distributed among different technical systems. The set must be installed and updated together, to reach a consistent state. (Note: In contrast to an update, patches can be applied to individual software components.) The product instances define the maximum allowed software component distribution of a product version.
A product instance can contain other product instances. Product instances can also be re-used across products and may contain one or more software components. One product instance (and the software component versions it contains) is always installed on one technical system, so it cannot be distributed across technical systems.
Software Components and Software Component Versions
Software components are always described in versions. Software components versions are the smallest entity that can be installed on a technical system. A software component version can be part of several product instances. It can require other software component versions to be installed as well. There are smaller shippable software entities than software component versions like support packages, patches, and notes. They always refer to the software component version that they change.
Product Systems
Product systems bundle product instances of one or more technical systems. They are needed for maintenance and planning. One technical system can be in multiple product systems (hub scenario), so dependencies are defined between product systems.
Logical Components
Logical components describe a function, and group the systems providing this functionality in roles. When business process planners and software maintenance staff talk about systems, they are typically not concerned with the technical details and overall layout of the system implementation. The systems may not even physically exist when the logical component is created.
For more information, see Managing Logical Components.
More Information
For introductory information about modeling SAP system landscapes for successful maintenance, see the Maintenance Planning Guide at http://scn.sap.com/docs/DOC-29495.