What happens if a nonrecoverable load is running when an online backup
is running? What would happen to the table and data if we have to use
that backup to restore the database?

First of all - load and backup can not run concurrently on the same
tablespaces. So if load is running the backup will have to wait (or
throw an error - not quite sure) and vice versa.
If the backup is run after the load you're fine - all the data is in
the image. If load was run after the backup the rollforward process
(which will most probaly follow a restore operation) will find the load
log records and will place the table in an unaccessible state. You will
have to redo your load after restore/rollforward (eventually you must
drop/recreate the table). To overcome this take a look at the COPY YES
option of load

HTH
Joachim

Thanks for your response. I understand the part that I will have to
reload the data that was loaded after the backup but why will I have to
drop and recreate the table? That will mean I will lose any data that
existed in the table even before this load started.

These are the drawbacks of a LOAD .. NONRECOVERABLE. A table that was
loaded that way ist not recoverable at all - even the data that existed
before load. Only when you backup the tablespace/database after the
LOAD operation you'll be able to restore the data.
I'm not sure at the moment if you'll have to drop/recreate the table in
case of a rollforward of a LOAD .. NONRECOVERABLE, but even if its not
necessary you need to use LOAD .. REPLACE to get access to the table
again (which means you will lose all the data which is already stored
in the table).
That's why I always recommend to use LOAD ... COPY YES on tables which
do already have data in it. Or not to use LOAD at all but IMPORT which
uses SQL INSERT and therefor logs everything.