Accessing multiple external subsystems

An application program can access DL/I and an external subsystem in the same execution. Whether or not an application program can access more than one external subsystem in the same execution can be restricted by the language interface.

Where the data (call) interface provided to application programs by one external subsystem (product) is distinct from the interface provided by another external subsystem (for example, DL/I calls as distinct from SQL calls), an application can access both subsystems because the language interface paths can be different. Where the data interface is the same, as in the case of two external subsystems of the same type (two instances of the external subsystem) or two external subsystem products that use the same call interface (for example, SQL), an application cannot access both in the same execution unless the application is written to be dependent on data location. (The dependency is intrinsic in the case of different call interfaces.)