以下是来自SAP官方实例的解释，SAP实例和数据库的实例类似。
Instances
Definition
SAP instances are defined during the installation of the SAP system.
Note
The term “instance” is often used synonymously with “server” or “application server” in the SAP system. This depends on the selected installation environment. You can install multiple instances on one application server.
An SAP instance defines a group of resources such as memory, work processes and so on, usually in support of a single application server or database server within a client/server environment. Application servers share the same memory areas and are controlled by the same dispatcher process.
An SAP instance is handled by CCMS as a unit. A user logs on to the SAP system using an instance.
An SAP system can consist of one or more instances, such as an SAP system with a single instance with only one central server or a client/server system with two or more separate instances.
For each SAP instance:
● Separate directories are defined on the UNIX, AS/400, or Microsoft Windows NT server on which the instance is to run
● Shared file systems can be used
● Entries are created in operating system configuration files (/etc/services, /etc/sapconfig…)
● Communication entries are created in the host
● Start and system profiles are created
● Operating system users are installed
Note
An SAP instance is not assigned automatically to an operation mode.