Using Version 8 Applications With Mimer SQL Version 9
Note: This chapter applies to Mimer SQL on Alpha/VMS and not Integrity, since no Mimer SQL version 8 was released there.
A Mimer SQL version 8 application is linked with the MIMDB8 shared library which provides client-side functionality for the application. The MIMDB8 shared library communicates with the database server.
The API exported by the MIMDB8 library is compatible with the MIMDB9 library. Likewise the client/server protocol used between the MIMDB8/MIMDB9 libraries and the database server is also compatible between versions. This means that there are several ways to run a Mimer SQL Engine version 8 application with a Mimer SQL Engine version 9 server.
Relink the Application
The preferred method is to relink the version 8 application with the MIMDB9 shared library. This will make the application a true version 9 application and eliminate the setup needed by the other approaches.
This is the preferred method if the sources or object files of the application is still available.
Remap the Shareable Libraries
By defining the logical name MIMDB8 to point to MIMDB9, all version 8 applications will use the MIMDB9 shared library$ DEFINE MIMDB8 MIMDB9
(Define the logical name in the SYSTEM or GROUP logical name tables as appropriate.)
This method is very similar to relinking the application, but requires extra setup. This setup will also affect all version 8 applications simultaneously, which may lead to undesired effects unless care is exercised.
Continue With the Old Shared Library
Since the client/server protocol used between the MIMDB8 shared library and the database server is compatible between version 8 and version 9, the old version 8 application can access the version 9 server directly. There is no need to do anything special to the version 8 application.
The drawback with this method is that new features, optimizations and bug corrections in the new MIMDB9 shared library will not be available to the application; it will function as it did before and rely on the compatibility of the client/server protocol.
This method works for all kinds of communication protocols available; shared-memory, TCP/IP and DECNET. There is no need to do anything special in the SQLHOSTS file for this to work.
However, be aware that if you should try to access a database in single-user mode, the MIMDB8 shared library will map the version 8 single-user library. This library will fail if it tries to open a version 9 database in single-user mode.
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