as you are on LDMS 9 with SP2 you are not able to differ at the rerun time of the task, to only install on machines that didn't installed the software. You can do this with 9.5, there it is configurable which devices should be considered for rerunning the task.
Maybe I missed something, but are you distributing the software by push or by policy?
There is one great affect if you would use policy based distribution:
You don't need to reschedule the task to refresh the ldap target. This is done automatically by the scheduler service within one hour by default.
(Set up a push task for distribution, if you want to, but you don't need the task. The software will be donwloaded to the client if this is configured in the delivery method.)
Create a new Software Distribution Task with a policy as delivery method, for example required installation.
Add your LDAP Target to the Task and schedule this one ONCE! (The LDAP Target can be empty)
Make sure your Agentconfiguration queries for policy updates maybe every 3 hours
Now add a client to your LDAP Group and wait what will happen.
What you will see, is that the software will be installed after latest 4 hours.
If you have a test environment, then you can reduce the policy polling in your agent configuration and change the value for query refresh on the core server under Configure --> Services --> Scheduler --> Interval between Query evaluations from 1 hour to 15 minutes. ONLY do this in a test environment!
thanks a lot schmiddi. That was what i was looking for. works like a charm... Now im setting up preffered servers for remote locations.
your welcome. Nice to hear that my suggestion worked for you.