问题
Help me understand how Global temporary table works
I have process which is going to be threaded and requires data visible only to that thread session. So we opted for Global Temporary Table.
Is it better to leave global temporary table not being dropped after all threads are completed or is it wise to drop the table. Call to this process can happen once or twice in a day.
Around 4 tables are required
回答1:
Oracle Temp tables are NOT like SQL Server #temp tables. I can't see any reason to continuously drop/create the tables. The data is gone on a per session basis anyways once the transaction or session is completed (depends on table creation options). If you have multiple threads using the same db session, they will see each other's data. If you have one session per thread, then the data is limited in scope as you mentioned. See example here.
回答2:
If you drop global temporary table and recreate it then it is not impacting to any database activities and server disk io activities because global temporary tables are created in temp tablespace where no archive is generating and not checkpoint is updating header of tempfile. Purpose of temporary table is only accurately maintained in this case.
来源：https://stackoverflow.com/questions/27694579/global-temporary-table