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SQLDeveloper’s “mystats.sql” equivalent

It just occurred to me that I haven’t blogged about SQLDeveloper yet, something I really need to change ;) This post covers SQLDeveloper 19.4, and although I don’t know exactly when the feature you are reading about was added I doubt it was in the latest release.

A little bit of background first

Sometimes the wait interface isn’t enough, so you need to dig a little deeper into the performance issue. In my opinion there are two layers inside Oracle when it comes to performance troubleshooting:

  • The Wait Interface provides valuable insights about session activity, especially when off-CPU and waiting
  • Session counters provide insights into ongoing operations at a lower level, and finer granularity

Tanel Poder’s post I linked to (yes, it’s from 2010, time flies!) provides an excellent introduction to the topic. His (session) snapper.sql script is one of my favourite and most heavily-used tools, especially when investigating an ongoing issue. Have a look at the Snapper landing page to get some more details and ideas about its many capabilities, it can do a LOT.

Adrian Billington’s mystats.sql tracks sessions counters as well, but it takes a different approach. The mystats.sql script works particularly well when you can sandwich a piece of (PL/)SQL between calls to mystats start and mystasts stop. I have been using it extensively for research and even managed to sneak a little improvement in ;)

Here is an example of mystat use. It captures session counters before and after the execution of a SQL statement and prints the delta. Have a look at the GitHub repository for more details about this very useful utility as I’m not going into the details…

SQL> @mystats start s=s

PL/SQL procedure successfully completed.

SELECT /*+ noparallel gather_plan_statistics  */
  2      oi.order_id,
    SUM(oi.unit_price * oi.quantity)
  4  FROM
  5      soe.orders         o,
  6      soe.order_items    oi
  7  WHERE
  8          o.order_id = oi.order_id
  9      AND o.delivery_type = 'Express'
 10  GROUP BY
 11      oi.order_id
 12  HAVING
    SUM(oi.unit_price * oi.quantity) > 45000
 14  ORDER BY
 15      2 DESC;

  ORDER_ID SUM(OI.UNIT_PRICE*OI.QUANTITY)
---------- ------------------------------
   1449606                          49324
    577982                          48606
    468019                          47970
   1977685                          46786
   1891120                          45347
   2310221                          45209

6 rows selected.

SQL> @mystats stop t=1

==========================================================================================
MyStats report : 26-MAY-2020 18:44:51
==========================================================================================


------------------------------------------------------------------------------------------
1. Summary Timings
------------------------------------------------------------------------------------------

Type    Statistic Name                                                               Value
------  ----------------------------------------------------------------  ----------------
TIMER   snapshot interval (seconds)                                                  14.76
TIMER   CPU time used (seconds)                                                       2.38


------------------------------------------------------------------------------------------
2. Statistics Report
------------------------------------------------------------------------------------------

Type    Statistic Name                                                               Value
------  ----------------------------------------------------------------  ----------------
STAT    CPU used by this session                                                       239
STAT    CPU used when call started                                                     238
STAT    CR blocks created                                                               13
STAT    DB time                                                                        692
STAT    Effective IO time                                                        4,415,766
STAT    Number of read IOs issued                                                    1,336
STAT    Requests to/from client                                                         20
STAT    SQL*Net roundtrips to/from client                                               20
STAT    application wait time                                                            9
STAT    buffer is not pinned count                                                       7
STAT    bytes received via SQL*Net from client                                      20,586
STAT    bytes sent via SQL*Net to client                                            10,594
STAT    calls to get snapshot scn: kcmgss                                              791
STAT    calls to kcmgcs                                                                 47
STAT    cell physical IO interconnect bytes                                  1,370,603,520
STAT    consistent changes                                                             944
STAT    consistent gets                                                            278,437
STAT    consistent gets direct                                                     167,309
STAT    consistent gets examination                                                    251
STAT    consistent gets examination (fastpath)                                         251
STAT    consistent gets from cache                                                 111,128
STAT    consistent gets pin                                                        110,877
STAT    consistent gets pin (fastpath)                                             110,876
STAT    data blocks consistent reads - undo records applied                            247
STAT    db block changes                                                               838
STAT    db block gets                                                                2,415
STAT    db block gets from cache                                                     2,415
STAT    db block gets from cache (fastpath)                                          1,970
STAT    dirty buffers inspected                                                         33
STAT    enqueue conversions                                                              4
STAT    enqueue releases                                                                 8
STAT    enqueue requests                                                                 8
STAT    enqueue waits                                                                    1
STAT    execute count                                                                   17
STAT    execute count                                                                   17
STAT    file io wait time                                                       10,452,219
STAT    free buffer inspected                                                          105
STAT    free buffer requested                                                           69
STAT    heap block compress                                                              2
STAT    hot buffers moved to head of LRU                                               193
STAT    index fetch by key                                                               2
STAT    lob writes                                                                     391
STAT    lob writes unaligned                                                           391
STAT    logical read bytes from cache                                          930,144,256
STAT    no work - consistent read gets                                             277,738
STAT    non-idle wait count                                                          1,153
STAT    non-idle wait time                                                             452
STAT    opened cursors cumulative                                                       21
STAT    parse count (hard)                                                               1
STAT    parse count (total)                                                             17
STAT    physical read IO requests                                                    1,337
STAT    physical read bytes                                                  1,370,603,520
STAT    physical read total IO requests                                              1,337
STAT    physical read total bytes                                            1,370,603,520
STAT    physical read total multi block requests                                     1,336
STAT    physical reads                                                             167,310
STAT    physical reads cache                                                             1
STAT    physical reads direct                                                      167,309
STAT    process last non-idle time                                                      15
STAT    recursive calls                                                              2,022
STAT    recursive cpu usage                                                              3
STAT    rollbacks only - consistent read gets                                           26
STAT    rows fetched via callback                                                        1
STAT    session cursor cache count                                                       7
STAT    session cursor cache hits                                                       10
STAT    session logical reads                                                      280,852
STAT    session pga memory                                                       2,276,704
STAT    session pga memory max                                                  65,518,944
STAT    session uga memory                                                         261,952
STAT    session uga memory max                                                  63,036,496
STAT    sorts (memory)                                                                   1
STAT    sorts (rows)                                                                     6
STAT    table fetch by rowid                                                             1
STAT    table scan blocks gotten                                                   277,764
STAT    table scan disk non-IMC rows gotten                                     31,341,195
STAT    table scan rows gotten                                                  31,341,195
STAT    table scans (direct read)                                                        1
STAT    table scans (long tables)                                                        2
STAT    temp space allocated (bytes)                                             1,048,576
STAT    user I/O wait time                                                             442
STAT    user calls                                                                      28
STAT    workarea executions - optimal                                                    6
STAT    workarea memory allocated                                                       12


------------------------------------------------------------------------------------------
3. Options Used
------------------------------------------------------------------------------------------
- Statistics types : s=s
- Reporting filter : t=1


------------------------------------------------------------------------------------------
4. About
------------------------------------------------------------------------------------------
- MyStats v3.0 by Adrian Billington (http://www.oracle-developer.net)
- Original version based on the SNAP_MY_STATS utility by Jonathan Lewis


==========================================================================================
End of report
==========================================================================================

PL/SQL procedure successfully completed.

I have modified mystats slightly so as to sort output by statistic name, rather than the change in value. I find it easier to read that way, but your mileage may vary.

Each time I look at performance instrumentation in the Oracle database I am pleasantly surprised about the level of detail available. I haven’t blogged about it lately, but going back a bit to 12.2 shows the progress made. And Oracle didn’t stop there, either. Using mystats’s output I can derive all sorts of interesting facts, none of which are of importance for this post as I’m purely interesting in reporting the change in session stats ;) When researching how Oracle works, this is quite a wealth of information, and you can find further examples on this blog.

SQLDeveloper can do this, too

If you are using SQLDeveloper and don’t want/need to use the command line, you can get something quite similar as well. Just enter your query into the text window, then hit F6 for “Autotrace”. In the lower part of your Autotrace results, you can see the change in session counters. If not, you may have to swipe the statistics pane into view using the mouse. Figure 1 shows an example:

autotrace and change in session stats - SQLDeveloper 19.4https://martincarstenbach.files.wordpress.com/2020/05/sqldeveloper-autot... 150w, https://martincarstenbach.files.wordpress.com/2020/05/sqldeveloper-autot... 300w, https://martincarstenbach.files.wordpress.com/2020/05/sqldeveloper-autot... 768w, https://martincarstenbach.files.wordpress.com/2020/05/sqldeveloper-autot... 1587w" sizes="(max-width: 1024px) 100vw, 1024px" />
Figure 1: SQLDeveloper’s Autotrace function displaying change in session statistics for this query

Summary

Session counters are super useful for understanding what Oracle does at a more granular level than the wait interface. For the most part, using the wait interface is enough, yet there is the occasional case where more details are needed. I often consider changes in session statistics when researching a particular problem, and thankfully I don’t have to come up with ways to do so as the community has already lent a helping hand!