mag@mutation_mutation > select * from v$version;

BANNER
----------------------------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
PL/SQL Release 9.2.0.4.0 - Production
CORE    9.2.0.3.0       Production
TNS for Solaris: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production

  1* create global temporary table mygtt (c1 varchar2(30)) on commit preserve rows
mag@mutation_mutation > /

Table created.

mag@mutation_mutation > set autotrace on stat ;

mag@mutation_mutation > insert into mygtt (select segment_name from dba_segments);

1159 rows created.

Statistics
----------------------------------------------------------
        403  recursive calls
       1194  db block gets
      12681  consistent gets
         17  physical reads
     149052  redo size
       1013  bytes sent via SQL*Net to client
       1070  bytes received via SQL*Net from client
          4  SQL*Net roundtrips to/from client
         14  sorts (memory)
          0  sorts (disk)
       1159  rows processed

--
-- the same operation in regular table will generate much lesser redo
-- 
 
mag@mutation_mutation > create table regular_table ( c1 varchar2(30));

Table created.

mag@mutation_mutation > insert into regular_table (select segment_name from dba_segments);

1160 rows created.

Statistics
----------------------------------------------------------
         23  recursive calls
         61  db block gets
      12587  consistent gets
          0  physical reads
      32696  redo size
       1019  bytes sent via SQL*Net to client
       1081  bytes received via SQL*Net from client
          4  SQL*Net roundtrips to/from client
          2  sorts (memory)
          0  sorts (disk)
       1160  rows processed