Sum of temp used from ASH view

I had a situation where I wanted to compare the temp space used by two similar insert statements on a test system.  One was filling up the temporary tablespace and the other wasn’t.

select sql_id,sample_time,
sum(TEMP_SPACE_ALLOCATED)/(1024*1024*1024) gig
from DBA_HIST_ACTIVE_SESS_HISTORY
where sample_time > sysdate-2
and TEMP_SPACE_ALLOCATED > (1*1024*1024*1024)
and sql_id in ('99m08n4dv67h9','8av0z21tm15as')
group by sql_id,sample_time
order by sql_id,sample_time;

SQL_ID        SAMPLE_TIME                      GIG
------------- ------------------------- ----------
8av0z21tm15as 21-SEP-12 10.20.49.279 AM 35.8271484
8av0z21tm15as 21-SEP-12 10.20.59.309 AM 44.6728516
8av0z21tm15as 21-SEP-12 10.21.09.329 AM 142.089844
8av0z21tm15as 21-SEP-12 10.21.19.379 AM 133.241211
8av0z21tm15as 21-SEP-12 10.21.29.389 AM 142.089844
8av0z21tm15as 21-SEP-12 10.21.39.399 AM 142.089844
99m08n4dv67h9 21-SEP-12 12.32.50.790 PM 43.2587891
99m08n4dv67h9 21-SEP-12 12.33.00.810 PM 88.3574219
99m08n4dv67h9 21-SEP-12 12.33.10.820 PM 100.229492
99m08n4dv67h9 21-SEP-12 12.33.20.840 PM 111.904297
99m08n4dv67h9 21-SEP-12 12.33.30.860 PM 147.005859

I used a query that I had posted about earlier where you can see how much temp space a query is using by querying the ASH.  But, in this case the two queries were parallel inserts so I summed the temp space used across all the sessions running the given sql_id.  In this case I knew there was only one running at a time.  If multiple were running I would have summed the temp space used by all the inserts with the same sql_id.  The dev team reported that the first sql_id wasn’t using any temp and the second was filling it up, but this query showed that they both were using more than 140 gig of temp at their peak.

– Bobby

P.S.  In retrospect I should have left off the TEMP_SPACE_ALLOCATED condition but at the peak all the parallel query servers probably had more than 1 gig of temp.  This was built from the previous query that only showed sessions with temp usage over 1 gig.  In this example I really wanted all the sessions for the given sql_ids even if they had less than 1 gig temp.  But, I’m leaving the query as it is because it was what I really ran and it was helpful.

About Bobby

I live in Chandler, Arizona with my wife and three daughters. I work for US Foods, the second largest food distribution company in the United States. I have worked in the Information Technology field since 1989. I have a passion for Oracle database performance tuning because I enjoy challenging technical problems that require an understanding of computer science. I enjoy communicating with people about my work.

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