RE: Rare huge surge in TEMP space usage

  • From: Dominic Brooks <dombrooks@xxxxxxxxxxx>
  • To: "frankagordon@xxxxxxxxx" <frankagordon@xxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 6 Dec 2018 10:09:52 +0000

Queries getting a suboptimal plan and then consuming vast amounts of temp due 
to poorly sized workareas?

Not unusual.



Real time SQL monitoring or raw ASH data will confirm which particular lines of 
the bad plan were responsible.



________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> on behalf 
of Frank Gordon <frankagordon@xxxxxxxxx>
Sent: Thursday, December 6, 2018 10:05:16 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Rare huge surge in TEMP space usage

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
--
https://eur04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.freelists.org%2Fwebpage%2Foracle-l&amp;data=02%7C01%7C%7C7ed695b4e4ec40b5bdf508d65b628f91%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636796876245487313&amp;sdata=00MErfwE%2FjfWWzw37uKtOvxz9xa%2FaJY%2FitQDl8LcLN8%3D&amp;reserved=0


Other related posts: