Chapter XVI Distributed PowerBuilder works
16.1 Virtual Machine
In this chapter, we describe in detail the working mechanism of Distributed PowerBuilder.
PowerBuilder in the server virtual machine model is achieved. Whenever a link to the client and server, the server for the client to open a separate memory, the formation of an independent virtual machine.
If we have four client applications to link to the server, PowerBuilder will set up four virtual machines, the four virtual machines are independent of each other, each with four different memory blocks, they are not directly between Sharing.
In addition, we need to point out that so far as to, PowerBuilder of all function calls are synchronous, which also includes the realization of Distributed PowerBuilder. When an application is called a proxy defined function, this application will be in a wait state until the service side of the NVO to final results to return. Before the return of the NVO, the application will be temporarily suspended the operating system.
PowerBuilder can not be directly shared memory, and the client and server session is synchronized.
16.2 remote call function parameters
Client call a remote NVO may use the function parameters. The function parameter can be any simple data type (Simple Data Types), including the structure, array, etc., reference method (By Reference) or directly by value (By Value) can be. PowerBuilder also supports NVO object parameters.
However, PowerBuilder does not support the use of the object pass parameters by reference. In PowerBuilder, there are a number of complex objects, such as the data window, window object and so on, we can not pass parameters by reference. This is a remote call parameters PowerBuilder restrictions.
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