Validity Checking Programs

I'm in the process of trying to write a utility that will capture which
parameters were specified when a command was executed so that they can be
reused as defaults the next time the command is run for the same object.
For example, when using the CRTPGM command for some objects I may have
binding directories specified, whilst for others I may list the service
programs and modules separately.

I thought about using Validity Checking Programs (VCP) assigned to the
particular commands that would log the parameters used in a database, but
this has raised a number of questions:

a) The documentation says that the parameters for the VCP need to be in
the same sequence as the Command Processing Program (CPP), however there's
no documentation anywhere on the parameters accepted by any given CPP. I
can prompt the command and see the available parameters, but there's nothing
to say that - for example - whether OUTPUT(*PRINT) passes "*PRINT" or "1" or
anything else to the CPP. I have found that by specifying two parameters
for a VCP, the first of 4 characters followed by a 1024 characters I can
substring the second parameter to find the details by trial and error. Does
anybody know if there is any documentation anywhere that shows what the
CPP's are expecting?

b) Secondly, when I assign a test VCP to a command the VCP only runs
when I prompt the command and press Enter. Is this the correct behaviour
for a VCP? I would have expected it to run every time the command is
executed.

c) Are there any API's that return compile time information? If, for
example, I compare the DSPMOD output with the QBNRMODI system API there are
a lot pieces of information missing from the API output.

Thanks

Jonathan