Clients per Gem

> In SAP S/4HANA discussions, I find two discussions of client. One uses terms like dev or prod. Another uses numbers like 100. What is the difference?

You're right, the term "client" in SAP S/4HANA can be confusing because it's used in two distinct contexts:

1. Logical Clients (Numbers like 100, 200, etc.):

• Definition: These are numerical clients within an SAP system. They represent separate, independent business entities or organizational units within the same physical SAP system.  
• Purpose:
  • Data Separation: Each client has its own master data, transactional data, and customizing settings. This means data in client 100 is completely separate from data in client 200.
  • Organizational Isolation: It allows different departments, subsidiaries, or even entirely separate companies to use the same SAP system without interfering with each other's data.
  • Testing and Development: Clients are often used for different purposes, such as:
    • Development (DEV): Client for configuring and customizing the system.
    • Quality Assurance (QA): Client for testing changes before they go live.
    • Production (PRD): Client for live business operations.
• Example:
  • Client 100 might be used for development and configuration.  
  • Client 200 might be used for testing.
  • Client 300 might be the live production system.

2. System Landscapes (DEV, QA, PRD):

• Definition: These terms refer to the different environments or stages of an SAP system's lifecycle. They represent the overall system landscape, which typically includes multiple physical or virtual servers.
• Purpose:
  • Software Development Lifecycle: They provide a structured approach to developing, testing, and deploying SAP changes.  
  • Risk Management: By separating development and testing from the production system, they minimize the risk of errors affecting live business operations.
  • Change Control: They allow for controlled and auditable changes to the SAP system.
• Common Landscape:
  • Development (DEV): Where developers make changes and configurations. This system will contain typically many clients for different types of development.
  • Quality Assurance (QA): Where testers validate changes before they are moved to production. The QA system will contain clients that closely reflect production client configuration.
  • Production (PRD): The live system used for day-to-day business operations. This system typically has a very strictly controlled single client, or a small number of production clients.
• Relationship to Logical Clients:
  • Each system landscape (DEV, QA, PRD) will contain one or more logical clients (numbers).
  • For example, the DEV system might have clients 100, 110, and 120, each used for different development tasks.
  • The PRD system will typically have client 300 which is the live production client.

In summary:

• Logical clients (numbers) are for data separation and organizational isolation within a single SAP system.  
• System landscapes (DEV, QA, PRD) are for managing the software development lifecycle and controlling changes across multiple SAP systems.

Therefore, when someone says "client 100," they're referring to a specific logical client within an SAP system. When someone says "the DEV client," they're referring to a logical client within the development system landscape.