In your case, temporary tables .... be it Global TT or Volatile TT .... wont work.
Because, for GTT it retains its definition across all sessions, but data is only visible to session that inserted it.
VTTs on the other hand, gets dropped as soon as session is disconnected which created them.
You should use permanent table for your task for the data to be available across multiple sessions.
Global temporary table base definition is stored in data dictionary. When you create a GTT, an instance of this base definition is created against the session. Temporary table instance will be dropped at the session termination. So when you disconnect the session, temp table is dropped.
If there is a compulsion to disconnect the session, then it would be difficult to use either Volatile or temp table. you can create a normal table and use it, and then drop it manually at the transaction end.
Thanks Adeel for your advice, and thanks Saeed for your help too. I was able to create a permanent table in EDW, and that solved it. You guys really rock!