CPYF lock?

Folks:

I'm working on a problem where we are having problems when using CPYF to add records to a file.

I was reviewing the help text for the CPYF command noticed something ...

During the time a CPYF request is run, the file specified for
the To file (TOFILE) parameter may be locked (similar to an
*EXCL lock with no timeout) so that no access is possible.

This has me somewhat confused ... what do they mean "may be locked" and "similar to an *EXCL lock"?

I tried doing a CPYF to a a file that was allocated with *SHRUPD, but the copy worked fine. The only way I was able to get CPYF to have a problem copying records was if allocated the object with *EXCL myself.

So the questions are ...

a) What determines if the target file is locked or not.
b) What kind of lock is put on the target file (if it's not exactly a *EXCL lock).
c) Is there a way to reproduce the lock so I can diagnose the problem?

Thanks!

david