I suspect you have a multitude of issues here.
In share you can only delete 50 at a time & if you try and delete the folder it will likely timeout and rollback.
Also, if you do succeed then you will end up with 30,000 items in the Trash and the same problem again.
In the assumption you only need to do this once, I can think of 3 possible solutions:-
1. Write a webscript that will find this folder, then for the first 100 child documents add sys:temporary the aspect and delete the document and then stop. Call that webscript manually from a webbrowser 300 times using some external scripting language 300 times. You may be able to delete more than 100 at a time before you run into transaction buffer size issues.
2. Write some Javavscript that will do the same and create a Quartz scheduled job that repeatedly calls it.
3. Write a Java Bean that will do the above but controll the transaction in the bean so you need to run it only once.
For a one off, 1 is probably easier. If you do not add sys:temporary then your 30,000 items will end up in the trash and you then have a problem deleting them from the trash (unless you are already running a trashcan cleaner).
