Cross-Debugging

Debugger Performance Considerations

A distributed file system makes it possible to develop your applications in a cross-development environment. In a distributed file system, programs can read or write files directly in a file system on a remote machine. The Network File System (NFS) client support provided by the SAS/C Connectivity Support Library allows the SAS/C Debugger to access files that do not reside on the mainframe at all. Additional information can be found in Using the NFS Client.

The main performance issue to consider when debugging in a cross-development environment is the time required by the debugger, which runs on the mainframe, to access files residing on the host workstation. In general, if you can reduce the number of times files that reside on the workstation are accessed by the debugger, performance will be improved.

One method of improving debugger performance is to use the set search command to direct the debugger to access files residing on the mainframe whenever possible. For example, when developing in a cross-development environment, it is likely that identical copies of the system include files will reside on both the host workstation and the target mainframe. You should use the set search systeminclude command to direct the debugger to use the system include files located on the target mainframe.

Another way to improve performance is to specify a debugger Source Window buffer that is large enough to hold the entire source file. This allows the debugger to keep the entire source file in mainframe memory for the time that the compilation is being debugged. Switching compilations causes the file to be flushed. As a guideline, the amount of memory needed to hold one source line is equal to the length of the line, after stripping trailing blanks, plus three bytes. Refer to documentation for the Config Window and the window memory command in the SAS/C Debugger User's Guide and Reference for more information about debugger window buffers.

Even though your source, include, and debugger files may reside on the host workstation, on systems that do not enjoy the advantages of a distributed file system, or if your situation requires you to minimize network traffic, it may be advantageous to use a file transfer mechanism, such as FTP, to copy some of these files to the target mainframe. For example, if you are debugging an application composed of many source files and you are only actively developing the code in one or two of those files, the performance of the debugger will be improved if the source files that will not require frequent changes and re-compilation reside on the target mainframe as well as the host workstation.

Similarly, you may use the set cache command to establish a cache location for your debugger file if you feel this appropriate for the application being debugged.

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