Parallel Hint, How is default different? Options

[jerry]

Hi,

Can somebody tell me the difference between the following parallel hint formats?

1. select /*+ PARALLEL*/ from emp;
2. select /*+ PARALLEL (t, default) from emp t;

I am seeing different results for each query.

Thanks
Jerry

[burleson]

Hi Jerry,

default value is two times the number of CPUs in your system

http://www.dba-oracle.com/art_builder_opq_cpu.htm

The danger is setting parallel at the database level with the ALTER TABLE command like this:


Alter table customer parallel degree 35;

The recommended approach for using Parallel query is to add a parallel hint to all SQL statements that perform a full-table scan and would benefit from parallel query.

select /*+ FULL(emp) PARALLEL(emp, 35) */

Here's an OTM discussion of parallel hints:

http://www.oracle.com/technology/oramag/we...bo_pt2_pt1.html