Type of the instantiation model of the MIDAS Program in Delphi (Midas 3)

The Application of "das" in DelphiProgramCOM server instantiation model type
(1) Internal instance
Create an in-process com program, that is, the DLL server.
(2) Single Instance
This model is used if each client program runs an instance of the server program. that is, each frontend program connected to IOT Platform runs a corresponding application server on the server. therefore, each query sent from the frontend has its own

It doesn't matter whether the queuing problem is handled by an independent process application, but it will occupy system resources and affect the overall running efficiency of the server.
(3) Multiple instance
This model is used if the client program shares the server program. an application server can process links of several front-end applications at the same time. The technical explanation is that all front-end applications can share a single process application service.

. The biggest advantage of this mode is that the activation and operation efficiency is fast, it does not consume too many system resources on the server, and it is easier to manage. however, it hides a problem that does not support multi-task processing. If a front-end user sends a query

Request, and the query results may be larger than MB. At this time, the query requirements sent by other online front-end users must wait until the previous query requirements have been completed and obtained accordingly, to continue running. this may take a lot of time,

In addition, if an error occurs in the query of a foreground program, other query requests queuing later will die.
Note: Which mode is used to create an application server? The answer is: depending on the system requirements. Simply put, you can create two groups of application servers, one in the multiple instance mode and the other in the single

Instance mode, but you must divide the program type into two types, one is to query a small amount of data or less important write operations, another write operation that queries large data volumes or important data. in this way, your foreground program can be placed

The two tdcomconection are connected to two application servers in different modes for different operations.