Re: Rare huge surge in TEMP space usage

  • From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Thu, 6 Dec 2018 22:18:58 -0500

Oh yes, I've seen plenty of those. That is a phenomenon known as "lousy query".  If it cannot be tuned the other way, I would break it into materialized views and use bitmap indexes on the MV's.

Regards

On 12/6/18 5:05 AM, Frank Gordon wrote:

Hello,

Oracle 12.1.0.2.0, Windows.

A query that ran properly for months, for a single day surged in it's
usage of TEMP space, we increased the TEMP space 5x and had to wait
for more disk to be allocated. During the waiting period the query
went back to normal.
The query is of the form

WITH t AS (select ... from tables WHERE ... group by everything),
     u AS (select ... from T, table  WHERE ..)
SELECT ... FROM tables, T, U

The "group by everything" is suspicious; as is the usage of the same
tables over and over again within the subquery factoring clauses.
Materialized views and subquery factoring also suspicious. HASH JOINS
also suspicious
In the plan a CARTESIAN JOIN is suspicious also.
Started looking at historical stats and 10046/10053 traces.

Anyone ever seen anything like this before?

Thanks,
Frank
--
http://www.freelists.org/webpage/oracle-l


--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217

--
http://www.freelists.org/webpage/oracle-l


Other related posts: