At each call of a POSIX program via the system call exec(), the following conditions will be tested in the order of priority indicated here:
Was the task created by fork?
Is debugging deactivated for the program?
Does a program cache exist for the session or for the user, or does a global program cache already exist? Is the corresponding program core image stored in the cache?
If one of these conditions is not fulfilled, the program will be loaded and started via BLS.
If all the conditions are fulfilled, the program core image stored in the program cache selected will be copied to memory and started directly, thus bypassing BLS.
Figure 30: Program cache available for a process
Bypassing BLS will result in the incomplete integration of a POSIX-started program in the BS2000 program environment. This will impose some restrictions on the programs loaded from the program cache. These restrictions include:
Entries defined in the program are not visible from the outside. This means that the program can dynamically load objects, but these objects cannot satisfy external links to the program.
No loading message is generated.
Testing with AID is not possible.
The program name in the /STATUS command output is missing
The debug command looses its function when it is loaded from the program cache. Thus, this command should not be loaded into the program cache.