Re: What is Parallel DML?

The short story is that you are going to get multiple server processes updating different data blocks at the same time. Accordingly, whatever DML it is that you are performing takes much less time to perform.

Totally pointless on a single CPU box, really, since only one process can run on a CPU at any one nanosecond, but in a multi-CPU and multi-Gigabyte database, it can make a lot of difference.

Regards
HJR "Dino Hsu" <dino1_at_ms1.hinet.net> wrote in message news:0lghlt4hu21jpal9rg24i8juvg9lnvghaq_at_4ax.com...
> Dear all,
>
> In a book, it says:
> "In Oracle, you have the power of parallel DML and query to speed your
> direct path along. In the code block that follows, notice the select
> statement has an embedded parallel query hint. Query and DML operation
> allows parallelism by generating multiple I/O processes that either
> draw more data into memory or write query. It requires that you first
> enable parallel DML in your session, using the alter session enable
> parallel DML statement, which must be executed at the beginning of the
> transaction if it is to be used at all during the transaction. The
> following code block demonstrates how you can mix and match hints in
> your direct-path insert statements:
>
> ALTER SESSION ENABLE PARALLEL DML;
>
> INSERT /*+APPEND */ INTO spanky.employees NOLOGGING
> (select /*+PARALLEL(athena.employees,4) */ *
> from athena.emplyees);
>
> INSERT /*+PARALLEL(spanky.empoyees,4) */ INTO spanky.employees
> NOLOGGING
> (select /*+PARALLEL(athena.employees,4) */ *
> from athena.employees);
> "
>
> I don't fully understand the purpose and significance of using
> parallel DML yet, can anyone further explain this? What is difference
> between 'with' and 'without' parallel DML? Thanks in advance.
>
> Dino
>
Received on Fri Jul 20 2001 - 23:47:58 CDT