Here are some more differences between command files and UDCs:

- command files can be variable record files, but UDCs cannot (since FPOINT
is
used in UDC processing).
- one needs read (or execute) and lock access to the UDC file, only read (or
execute)
access is needed for command files.
- the end-of-UDC command is indicated by one or more asterisks (*) starting
in
column one (except for the last UDC in the file), the end of a script is the
EOF.
- UDCs have a filename and a command name, command files have just their
filename.
- Command files can reside in the POSIX name space, UDC files must be MPE
names.
- UDC command names can be up to 16 characters, command file names follow
the
rules for MPE or POSIX filenames.

Others have done a great job pointing out other major differences.

> Behalf Of Glenn J. Koster, Sr.
...
> 2.  UDC's have multiple options (OPTION LOGON, NOBREAK, etc.)
> which are not available to command files.

OPTION BREAK is supported in command files.

> 3.  UDC's can be set (must be set?) at any of three levels.  However,
> command files can be called / executed by anyone who has the
> appropriate access.

UDCs must be set at a level and the default level is USER.  UDCs can be set
at the system or account levels too.  The search order within UDCs is
different at logon than during normal execution.  At logon SYSTEM UDCs are
searched first, followed by ACCOUNT UDCs, followed by USER UDCs.  During
normal,
execution this order is reversed: USER UDCs are searched first, followed by
ACCOUNT
UDCs, followed by SYSTEM level UDCs.
...
> IMHO, command files add a great deal of flexibility, with relatively
> little overhead.  The only drawback is security, but a properly
> constructed command file can correct any associated security risks.

Command files can have READ access removed as long as the user is granted
eXecute access -- same for the UDC file.  The UDC file can be lockworded and
the caller does not need to know the lockword (the person executing
SETCATALOG
needs to know the lockword).  If a command file is lockworded, the lockword
must be provided every time the script is executed.

> The  ONLY drawbacks that I have to using command files are the OPTIONS
> and the length lacks the ability to be descriptive.  I only use UDC'S
> when I absolutely must control the command via one of these options or
> when an 8 character file name is not descriptive enough.

It is fairly common to create a short logon UDC that simply invokes a
command file to do all the work.

HTH,

Jeff Vance, CSY

p.s.  I am using MS Outlook.  If the format of my reply is odd or not useful
please let me know how to improve it.  Thanks!