Need help in Bulk collect

Question

Hi All,
I need a help to create a bulk statement. Please find the scenario below
I would like to copy a table A from table B using bulk collect also the table A has more records (1Million). Before doing this I need to either truncate the table B or drop the table to load the data from table A.
Please provide me the correct statement to achieve this request. Thanks in advance!!
Regards,
Boovan.

Answer 1

disabling any indexes on the target should be looked at first. If there are none then look at the above.
When you do a direct path load the indexes are build after loading.The point is that the direct path load does not avoid the undo due to the indexes.
In this example on a table with no indexes the undo used goes from 216kb to 16kb using append.
When an index is added the undo used goes up from 216kb to 704kb an increase of 488kb for a standard insert.
For the direct path insert the undo goes up from 16kb to 440kb so almost the full amount of undo due to the index.
So the presence of a single index can have a much greater impact on the amount of undo required than the use of a direct path load and that undo may not be avoided by the use of a direct path load unless the index is disabled beforehand.
Also note the tiny amounts of undo we are talking about for 50k rows.
SQL> create table t as select * from all_objects where 0 = 1;
Table created.
SQL> insert into t select * from all_objects;
56108 rows created.
SQL> select
  2      used_ublk undo_used_blk,
  3      used_ublk * blk_size_kb undo_used_kb,
  4      log_io logical_io,
  5      cr_get consistent_gets
  6  from
  7      v$transaction, v$session s,
  8      (select distinct sid from v$mystat) m,
  9      (select to_number(value)/1024 blk_size_kb
10          from v$parameter where name='db_block_size')
11  where
12      m.sid       =   s.sid
13  and ses_addr    =   saddr;
UNDO_USED_BLK UNDO_USED_KB LOGICAL_IO CONSISTENT_GETS
           27          216      13893         1042736
SQL> rollback;
Rollback complete.
SQL> insert /*+ append */ into t select * from all_objects;
56108 rows created.
SQL> select
  2      used_ublk undo_used_blk,
  3      used_ublk * blk_size_kb undo_used_kb,
  4      log_io logical_io,
  5      cr_get consistent_gets
  6  from
  7      v$transaction, v$session s,
  8      (select distinct sid from v$mystat) m,
  9      (select to_number(value)/1024 blk_size_kb
10          from v$parameter where name='db_block_size')
11  where
12      m.sid       =   s.sid
13  and ses_addr    =   saddr;
UNDO_USED_BLK UNDO_USED_KB LOGICAL_IO CONSISTENT_GETS
            2           16       1307         1041151
SQL> rollback;
Rollback complete.
SQL> create unique index t_idx on t (object_id);
Index created.
SQL> insert into t select * from all_objects;
56109 rows created.
SQL> select
  2      used_ublk undo_used_blk,
  3      used_ublk * blk_size_kb undo_used_kb,
  4      log_io logical_io,
  5      cr_get consistent_gets
  6  from
  7      v$transaction, v$session s,
  8      (select distinct sid from v$mystat) m,
  9      (select to_number(value)/1024 blk_size_kb
10          from v$parameter where name='db_block_size')
11  where
12      m.sid       =   s.sid
13  and ses_addr    =   saddr;
UNDO_USED_BLK UNDO_USED_KB LOGICAL_IO CONSISTENT_GETS
           88          704      20908         1043193
SQL> rollback;
Rollback complete.
SQL> insert /*+ append */ into t select * from all_objects;
56109 rows created.
SQL> select
  2      used_ublk undo_used_blk,
  3      used_ublk * blk_size_kb undo_used_kb,
  4      log_io logical_io,
  5      cr_get consistent_gets
  6  from
  7      v$transaction, v$session s,
  8      (select distinct sid from v$mystat) m,
  9      (select to_number(value)/1024 blk_size_kb
10          from v$parameter where name='db_block_size')
11  where
12      m.sid       =   s.sid
13  and ses_addr    =   saddr;
UNDO_USED_BLK UNDO_USED_KB LOGICAL_IO CONSISTENT_GETS
           57          456       2310         1041047