As part of the research I did for the 2nd edition of our Exadata book I used session statistics quite heavily. Session statistics can provide additional insights in situations where the wait interface on its own doesn’t get you any further.
On the command line, my tools of choice are either Tanel Poder’s excellent Session Snapper or Adrian Billington’s mystats utility. There are of course others, it just so happened that I’ve been using the previous two quite heavily. If you prefer a graphical front-end such as SQL Developer, you can grab the change in session statistics easily as described in an earlier post.
I’m not sure why it never occurred to me to check if SQL Developer’s best friend, sqlcl, has the same functionality. Well it does, and that’s great news. The other great news is that you can download sqlcl directly from Oracle’s website now.
Downloading SQLcl the new way
The first step to complete is to pull the latest version of sqlcl. Many thanks to Connor McDonald who told me there is a super-easy way to always get the latest version. Just use the following URL:
https://download.oracle.com/otn_software/java/sqldeveloper/sqlcl-latest.zip
Great! I don’t even need to worry about the version:
$ wget https://download.oracle.com/otn_software/java/sqldeveloper/sqlcl-latest.zip --2021-06-10 14:37:29-- https://download.oracle.com/otn_software/java/sqldeveloper/sqlcl-latest.zip Resolving download.oracle.com (download.oracle.com)... 104.76.200.85 Connecting to download.oracle.com (download.oracle.com)|104.76.200.85|:443... connected. HTTP request sent, awaiting response... 200 OK Length: 36960602 (35M) [application/zip] Saving to: ‘sqlcl-latest.zip’ sqlcl-latest.zip 100%[====================================>] 35.25M 6.35MB/s in 5.7s 2021-06-10 14:37:35 (6.19 MB/s) - ‘sqlcl-latest.zip’ saved [36960602/36960602]
Note that I’m downloading sqlcl-latest.zip, which translates to 21.1.1.113.1704 at the time of writing:
$ cd sqlcl/bin && ./sql -V SQLcl: Release 21.1.1.0 Production Build: 21.1.1.113.1704
With the latest sqlcl release unzipped it’s time to grab some session statistics.
Session Statistics, please!
To keep matters reasonably simple I’m using a non-partitioned table for my demonstration. As always, my examples use the excellent Swingbench (Order Entry) benchmark schema. Once connected to the database, I can start investigating. By the way I’m running this query on Oracle 19c in a VM on my laptop.
The first step is to enable auto-trace as shown here:
SQL> show version
Oracle SQLDeveloper Command-Line (SQLcl) version: 21.1.1.0 build: 21.1.1.113.1704
SQL> help set autotrace
SET AUTOTRACE
SET AUTOT[RACE] {OFF|ON|TRACE[ONLY]}
SQL> set autotrace on
Autotrace Enabled
Shows the execution plan as well as statistics of the statement.
Let’s run a query against the orders table:
SQL> select count(*) from soe.orders;
COUNT(*)
___________
17157480
Explain Plan
-----------------------------------------------------------
Plan hash value: 508073128
----------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time |
----------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 62161 (1)| 00:00:03 |
| 1 | SORT AGGREGATE | | 1 | | |
| 2 | TABLE ACCESS FULL| ORDERS | 17M| 62161 (1)| 00:00:03 |
----------------------------------------------------------------------
Statistics
-----------------------------------------------------------
103 CPU used by this session
104 CPU used when call started
209348 Cached Commit SCN referenced
4 Commit SCN cached
510 DB time
4171496 Effective IO time
3587 Number of read IOs issued
42 Requests to/from client
42 SQL*Net roundtrips to/from client
2 buffer is not pinned count
587 bytes received via SQL*Net from client
79087 bytes sent via SQL*Net to client
3 calls to get snapshot scn: kcmgss
8 calls to kcmgcs
1870921728 cell physical IO interconnect bytes
4 cleanout - number of ktugct calls
4 cleanouts only - consistent read gets
4 commit txn count during cleanout
228394 consistent gets
228384 consistent gets direct
4 consistent gets examination
4 consistent gets examination (fastpath)
10 consistent gets from cache
6 consistent gets pin
6 consistent gets pin (fastpath)
1 cursor authentications
2 enqueue releases
2 enqueue requests
2 execute count
6884470 file io wait time
4 immediate (CR) block cleanout applications
81920 logical read bytes from cache
228380 no work - consistent read gets
7233 non-idle wait count
418 non-idle wait time
2 opened cursors cumulative
1 opened cursors current
1 parse count (hard)
2 parse count (total)
1 parse time elapsed
3587 physical read IO requests
1870921728 physical read bytes
3587 physical read total IO requests
1870921728 physical read total bytes
3578 physical read total multi block requests
228384 physical reads
228384 physical reads direct
6 process last non-idle time
1 recursive calls
228394 session logical reads
1 sorts (memory)
2010 sorts (rows)
228384 table scan blocks gotten
17157480 table scan disk non-IMC rows gotten
17157480 table scan rows gotten
1 table scans (direct read)
1 table scans (long tables)
418 user I/O wait time
43 user calls
SQL>
This is pretty nifty in my opinion. There’s an execution plan and a whole raft of relevant session statistics.
I wouldn’t trust the execution plan too much as it’s generated by an “explain plan for” statement as a reader pointed out. So I guess I’ll still use Tanel’s tpt-oracle scripts for more accurate information.
Happy Troubleshooting!
