SORT_AREA_SIZE follow up

Question

I am using this query in my instance to determine the % of sorts done in memory.
select name, value from v$sysstat
where name like '%sort%';
Now we run other processes in this instance besides OLAP builds and I am curious if this query is good enough to give me a good look at how many disk sorts the OLAP is responsible for. I seem to be 99.99% sorting in memory.
If I ran this query before a build and then right after using only the diffs between the 2 queries would that give me a better idea of performance?

Answer 1

Hi ZeroWing,
What I normally do to monitor performance during an OLAP build is to schedule a whole series of queries to capture the following information:
   olap_waits            - collects and records information about OLAP wait events
   aw_read_writes        - collects and records information about temp, lob, cache writes and rows processed
   aw_long_ops           - collects and records information about long operations being performed within the AW
   aw_buffer_cache       - collects and records information about use of the buffer cache
   aw_cursor_parameters  - collects and records information about cursor usage
   aw_pga_performance    - collects and records information about pga performance
   aw_session_resouces   - collects and records information about session usage for a specific user
   aw_size               - collects and records information about size of aws for a specific user
   aw_sorts              - collects and records information about sort activity
   aw_redo_log_buffer    - collects and records information about redo and log buffer activity activity
   aw_ts_read_writes     - collects and records information about read/write activity for tablespaces and datafiles
   aw_segment_stats      - collects and records information about object segement statistics for a specific userI run these jobs via the database scheduler at regular intervals whilst a build is running. Each query inserts its results into a fact table so I can analyze the results once the load has finished. This fact table is then joined with the XML Load Log table. This allows me to match specific events within XML Load Log with system and instance statistics.
I am not sure what impact collecting all this information has on the overall performance of the instance (hopefully it is minimal?) but it does provide interesting information. At the moment I am still refining the info I collect and structure of the AW.
Keith Laker
Oracle EMEA Consulting
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