Re: Quick questions on direct insert, undo and parallel prosessing

Comments below:

Anurag Varma

"John" <jbradshaw777_at_yahoo.com> wrote in message news:f2f59d82.0310221432.50cc341f_at_posting.google.com...
> Hi groups,
>
> A few quick confirmations of sort...
> 1. Direct load insert WILL always generate redo IF ORACLE is in
> ARCHIVELOG mode.

direct load insert will generate redo .. albeit minimum. Discard your if condition.

> 2. Parallel query processing will not happen (regardless of how your
> table, database is set up) unless you you hint it in your queries.
Not exactly true:
Consider this example (Note: Your database init.ora parameters need to be set properly for this to work):
SQL> create table xyz (a number) parallel 4;

Table created.

SQL> insert into xyz select rownum from user_objects;

2032 rows created.

SQL> commit;

Commit complete.

SQL> set autotrace traceonly exp
SQL> select * from xyz;

Execution Plan

   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=1 Card=82 Bytes=1066)
   1    0   TABLE ACCESS* (FULL) OF 'XYZ' (Cost=1 Card=82 Bytes=1066)                                         :Q863000


   1 PARALLEL_TO_SERIAL            SELECT /*+ NO_EXPAND ROWID(A1) */ A1."A" FRO
                                   M "XYZ" PX_GRANULE(0, BLOCK_RANGE, D

> 3. Undo tablespace is created more for the purpose of supporting
> flash-back query than for the purpose of automating rollback
> management. It does not offer any improvemnet on the chance of you
> hitting the ORA-01555.

Not exactly true. Undo does not mean that you won't see 1555's at all. However, if set properly, it should minimize their occurence, if not eliminate them.

Also, although Oracle suggests that automatic undo be enabled before using this feature, I think it should work even with the old way of rollback segments.

>
> TIA.
>
> John
Received on Wed Oct 22 2003 - 21:21:48 CDT