DELR depends on a previous LSTR (for the recording number).
DELT, MODT and UPDT depend on a previous LSTT (for the timer number).
MODC depends on a previous LSTC (for the channel number).
HITKs from different connections could lead to complete confusion.
Just one example: SVDRP connection A does LSTT and gets a list of,
say, 5 timers. Connection B does the same and decides to delete timer
number 2. Now connection A does a MODT on timer 3 - well, at least what
it thought was timer 3, because that is now what used to be timer 4.
So it just isn't that simple...
Seems we both wrote another mesasge at the same time. My approach would
be to use unique ids for everything where a number is currently used.