If someone wants to load lots of data into the GTT, based on the 1M extent size, doesn't this seem to be inefficient and may pose a performance issue due to Oracle has to keep extending? I guess that if one wants to load lots of data (i.e. 1G+ data) into GTT, there might be other options rather than GTT.
From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
Subject: Re: problem about full scan temporary table
Date: Sun, 24 Sep 2006 11:40:58 +0100
>The space of the private copy of the temporary table is allocated in
>the temporary tablespace - so it is
>allocated one extent at a time as you need the space,
>and extra extents are allocated as each extent becomes
>By default, the temporary tablespace is locally managed with
>uniform extents of 1MB.
>The Co-operative Oracle Users' FAQ
>Cost Based Oracle: Fundamentals
>----- Original Message ----- From: "qihua wu" <wqhhp@xxxxxxxxx>
>To: <jonathan@xxxxxxxxxxxxxxxxxx>; <oracle-l@xxxxxxxxxxxxx>
>Sent: Sunday, September 24, 2006 11:36 AM
>Subject: RE: problem about full scan temporary table
>>Thanks for your reply, and I have a question based on
>>How does oracle know certain session will insert how
>>much data into the GTT?
>>Suppose the session first inserts 1 row, and 10
>>minutes later, inserts
>>another 1,000,000 rows. So at the beginning to operate
>>the GTT, how much
>>space will be allocated? If the space one session
>>occupied is not
>>continuous, then I don't think HWM makes much sense.