An SQL Tuning Methodology
Note: This is just one of the various ways I capture and tune SQL. I use many different methods to capture suboptimal SQL depending on the urgency of the situation and the details I require to grab the SQL and work on a solution. It is not all encompassing. Db2 Design Advisor is your friend, and in my experience is not used enough!!! But the hard part comes when you have captured a suboptimal SQL and Design Advisor doesn’t have any recommendations!!!! At this point you can’t just throw your hands up and give up, it has to be fixed!!! This is where we shine with our clients, there isn’t an SQL out there that we can’t improve using all of the knowledge we have and all the tools in our toolbox. I’ll post more on SQL rewrite possibilities, index design and redesign, how to capture suboptimal SQL, statistics effects on optimization, statistical views, informational constraints, and hints, to name a few….
- Connect to database and run “db2 call monreport.pkgcache” to get top statements.
— Command options —
CACHE_INTERVAL: All statements
SECTION_TYPE: Dynamic and static SQL
MEMBER: All
================================================================================
Part 1 – Summaries by ‘top’ metrics
Top 10 statements by TOTAL_CPU_TIME
——————————————————————————–
# TOTAL_ STMT_TEXT
CPU_TIME
— ———– —————————————————————
1 217980426 INSERT INTO SPECTRUM_RESULT_5GHZ (WHEN,MEAS_ID_FK,EYE_ID,ANT_ID
2 137210647 select MEAS_ID from final table (INSERT INTO CLIENT_PCAP_RADIO
3 33451937 INSERT INTO SCAN_RADIO (NW_ID, AP_ID, EYE_ID, ANT_ID, CHANNEL,
4 24715177 INSERT INTO SPECTRUM_RESULT (WHEN,MEAS_ID_FK,EYE_ID,ANT_ID,SUBC
5 24691176 select MEAS_ID from final table (INSERT INTO RADIO_ENVIRONMENT_
6 18695817 INSERT INTO AP_FTP_QOS_TEST (WHEN,MEAS_ID,NW_ID,AP_ID,EYE_ID,AN
7 17015041 select MEAS_ID from final table (INSERT INTO AP_PCAP_RADIO (WHE
8 16529630 select MEAS_CATEGORY_ID from final table (INSERT INTO AP_FTP_QO
9 8262363 select MEAS_ID from final table (INSERT INTO CLIENT_PCAP_QOS (W
10 4794274 select MEAS_CATEGORY_ID from final table (INSERT INTO MOS_QOS_T
- Go to topsql.sql script to get full SQL for above insert:
2017-09-22-13.09.08.775452 14586120 14586087
0 5465 14507 1
1 2 2 2 INS
ERT INTO SCAN_RADIO (NW_ID, AP_ID, EYE_ID, ANT_ID, CHANNEL, HT_MODE, BEACON_OK,
SIGNAL_LEVEL_APEYE, SNR_APEYE, QUALITY, MAXQUAL, DURATION, WHEN ) VALUES ( ?, ?,
?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ? )
- Then format the SQL for explain design advisor usage:
INSERT INTO CARAT7.SCAN_RADIO (NW_ID, AP_ID, EYE_ID, ANT_ID, CHANNEL,
HT_MODE, BEACON_OK,
SIGNAL_LEVEL_APEYE, SNR_APEYE, QUALITY,
MAXQUAL, DURATION, WHEN )
VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ? );
- Run db2advis [db7sign@east1 ~]$ db2advis -d meas7 -i iscanradio.txt | more
Using user id as default schema name. Use -n option to specify schema
execution started at timestamp 2017-09-22-12.35.55.976835
found [1] SQL statements from the input file
Recommending indexes…
0 indexes in current solution
[ 11.0000] timerons (without recommendations)
[ 11.0000] timerons (with current solution)
[0.00%] improvement
—
—
— LIST OF RECOMMENDED INDEXES
— ===========================
— no indexes are recommended for this workload.
—
—
— RECOMMENDED EXISTING INDEXES
— ============================
—
—
— UNUSED EXISTING INDEXES
— ============================
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_WHEN”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APEYEWHENBEACON”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APBEACONWHENNWSIG”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EYENWBEACONWHENSIG”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APNWBEACONWHENSIG”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_NWBEACONWHENSIG”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APBEACONWHENNWSNR”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APNWBEACONWHENSNR”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_NWBEACONWHENSNR”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EYENWBEACONWHENSNR”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APBEACONWHENNWCH”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_NWBEACONWHENCH”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EYENWBEACONWHENCH”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APNWWHENBEACON”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EYENWWHENBEACONAP”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_WHENEYESIGHTCHANTAP”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APEYEANTBEACONWHENSNR”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EYEANTBEACONWHENSNR”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EYECHBEACONWHENSNR”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_APWHENNWBEACON”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_CH_ANTID_APID_DBI3”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EID_ANTID_APID_CH_DBI3”;
— DROP INDEX “CARAT7 “.”I_SCAN_RADIO_EYEWHEN”;
— ===========================
—
0 record(s) selected.
- Review output and determine if index recommended or if not possible SQL rewrite or further manual analysis.
- Review unused indexes on the table in question.
[db7sign@east1 ~]$ db2 “select lastused, indname from syscat.indexes where tabname=’SCAN_RADIO'” | more
LASTUSED INDNAME
———- ———————————————————————
———————————————————–
09/21/2017 I_SCAN_RADIO_WHEN
09/22/2017 I_SCAN_RADIO_APEYEWHENBEACON
04/20/2017 I_SCAN_RADIO_APBEACONWHENNWSIG
04/17/2017 I_SCAN_RADIO_EYENWBEACONWHENSIG
09/22/2017 I_SCAN_RADIO_APNWBEACONWHENSIG
03/10/2017 I_SCAN_RADIO_NWBEACONWHENSIG
04/20/2017 I_SCAN_RADIO_APBEACONWHENNWSNR
11/04/2016 I_SCAN_RADIO_APNWBEACONWHENSNR
09/01/2017 I_SCAN_RADIO_NWBEACONWHENSNR
03/25/2017 I_SCAN_RADIO_EYENWBEACONWHENSNR
09/15/2017 I_SCAN_RADIO_APBEACONWHENNWCH
09/22/2017 I_SCAN_RADIO_NWBEACONWHENCH
09/08/2017 I_SCAN_RADIO_EYENWBEACONWHENCH
09/21/2017 I_SCAN_RADIO_APNWWHENBEACON
09/22/2017 I_SCAN_RADIO_EYENWWHENBEACONAP
09/07/2017 I_SCAN_RADIO_WHENEYESIGHTCHANTAP
03/31/2017 I_SCAN_RADIO_APEYEANTBEACONWHENSNR
09/14/2017 I_SCAN_RADIO_EYEANTBEACONWHENSNR
03/31/2017 I_SCAN_RADIO_EYECHBEACONWHENSNR
09/21/2017 I_SCAN_RADIO_APWHENNWBEACON
09/22/2017 I_SCAN_RADIO_CH_ANTID_APID_DBI3
09/22/2017 I_SCAN_RADIO_EID_ANTID_APID_CH_DBI3
09/22/2017 I_SCAN_RADIO_EYEWHEN
23 record(s) selected.
- Review index definitions and compare to query.
Index Index Unique Number of Index Index Null Index Data Max Varchar Xml BUSINESS_TIME Column
schema name rule columns type partitioning keys ID type Hashed Length pattern WITHOUT OVERLAPS names
——————————————————————————————————————————– ——————————————————————————————————————————– ————– ————– ————————— ————– —— ————— ——————————————————————————————————————————– ——- ————— ——————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————– ——————– ——————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————–
CARAT7 I_SCAN_RADIO_WHEN D 1 RELATIONAL DATA – Y 1 – – – – NO +WHEN
CARAT7 I_SCAN_RADIO_APEYEWHENBEACON D 4 RELATIONAL DATA – Y 2 – – – – NO +AP_ID+EYE_ID+WHEN+BEACON_OK
CARAT7 I_SCAN_RADIO_APBEACONWHENNWSIG D 5 RELATIONAL DATA – Y 3 – – – – NO +AP_ID+BEACON_OK+WHEN+NW_ID+SIGNAL_LEVEL_APEYE
CARAT7 I_SCAN_RADIO_EYENWBEACONWHENSIG D 5 RELATIONAL DATA – Y 4 – – – – NO +EYE_ID+NW_ID+BEACON_OK+WHEN+SIGNAL_LEVEL_APEYE
CARAT7 I_SCAN_RADIO_APNWBEACONWHENSIG D 5 RELATIONAL DATA – Y 5 – – – – NO +AP_ID+NW_ID+BEACON_OK+WHEN+SIGNAL_LEVEL_APEYE
CARAT7 I_SCAN_RADIO_NWBEACONWHENSIG D 4 RELATIONAL DATA – Y 6 – – – – NO +NW_ID+BEACON_OK+WHEN+SIGNAL_LEVEL_APEYE
CARAT7 I_SCAN_RADIO_APBEACONWHENNWSNR D 5 RELATIONAL DATA – Y 7 – – – – NO +AP_ID+BEACON_OK+WHEN+NW_ID+SNR_APEYE
CARAT7 I_SCAN_RADIO_APNWBEACONWHENSNR D 5 RELATIONAL DATA – Y 8 – – – – NO +AP_ID+NW_ID+BEACON_OK+WHEN+SNR_APEYE
CARAT7 I_SCAN_RADIO_NWBEACONWHENSNR D 4 RELATIONAL DATA – Y 9 – – – – NO +NW_ID+BEACON_OK+WHEN+SNR_APEYE
CARAT7 I_SCAN_RADIO_EYENWBEACONWHENSNR D 5 RELATIONAL DATA – Y 10 – – – – NO +EYE_ID+NW_ID+BEACON_OK+WHEN+SNR_APEYE
CARAT7 I_SCAN_RADIO_APBEACONWHENNWCH D 5 RELATIONAL DATA – Y 11 – – – – NO +AP_ID+BEACON_OK+WHEN+NW_ID+CHANNEL
CARAT7 I_SCAN_RADIO_NWBEACONWHENCH D 4 RELATIONAL DATA – Y 12 – – – – NO +NW_ID+BEACON_OK+WHEN+CHANNEL
CARAT7 I_SCAN_RADIO_EYENWBEACONWHENCH D 5 RELATIONAL DATA – Y 13 – – – – NO +EYE_ID+NW_ID+BEACON_OK+WHEN+CHANNEL
CARAT7 I_SCAN_RADIO_APNWWHENBEACON D 4 RELATIONAL DATA – Y 14 – – – – NO +AP_ID+NW_ID+WHEN+BEACON_OK
CARAT7 I_SCAN_RADIO_EYENWWHENBEACONAP D 5 RELATIONAL DATA – Y 15 – – – – NO +EYE_ID+NW_ID+WHEN+BEACON_OK+AP_ID
CARAT7 I_SCAN_RADIO_WHENEYESIGHTCHANTAP D 7 RELATIONAL DATA – Y 16 – – – – NO +WHEN+EYE_ID+SIGNAL_LEVEL_APEYE+HT_MODE+CHANNEL+ANT_ID+AP_ID
CARAT7 I_SCAN_RADIO_APEYEANTBEACONWHENSNR D 6 RELATIONAL DATA – Y 17 – – – – NO +AP_ID+EYE_ID+ANT_ID+BEACON_OK+WHEN+SNR_APEYE
CARAT7 I_SCAN_RADIO_EYEANTBEACONWHENSNR D 5 RELATIONAL DATA – Y 18 – – – – NO +EYE_ID+ANT_ID+BEACON_OK+WHEN+SNR_APEYE
CARAT7 I_SCAN_RADIO_EYECHBEACONWHENSNR D 5 RELATIONAL DATA – Y 19 – – – – NO +EYE_ID+CHANNEL+BEACON_OK+WHEN+SNR_APEYE
CARAT7 I_SCAN_RADIO_APWHENNWBEACON D 4 RELATIONAL DATA – Y 20 – – – – NO +AP_ID+WHEN+NW_ID+BEACON_OK
CARAT7 I_SCAN_RADIO_CH_ANTID_APID_DBI3 D 4 RELATIONAL DATA – Y 21 – – – – NO +CHANNEL+ANT_ID+WHEN+AP_ID
CARAT7 I_SCAN_RADIO_EID_ANTID_APID_CH_DBI3 D 4 RELATIONAL DATA – Y 22 – – – – NO +EYE_ID+ANT_ID+CHANNEL+AP_ID
CARAT7 I_SCAN_RADIO_EYEWHEN D 2 RELATIONAL DATA – Y 23 – – – – NO +EYE_ID-WHEN
- Get additional index usage data from tcbstats.
Index usage analysis from tcbstats:
TCB Index Stats:
Address TableName IID PartID EmpPgDel RootSplits BndrySplts PseuEmptPg EmPgMkdUsd Scans IxOnlyScns KeyUpdates InclUpdats NonBndSpts
PgAllocs Merges PseuDels DelClean IntNodSpl
0x00007F99D34C6EE0 SCAN_RADIO 25 n/a 0 0 9 0 0 550 328 0 0 134928 136332 0 0 0
1395
0x00007F99D34C6EE0 SCAN_RADIO 24 n/a 0 0 0 0 0 66 66 0 0 133191 133986 0 0 0
795
0x00007F99D34C6EE0 SCAN_RADIO 23 n/a 0 0 39 0 0 215 204 0 0 243578 247262 0 0 0
3645
0x00007F99D34C6EE0 SCAN_RADIO 22 n/a 0 0 31 0 0 120 120 0 0 241152 245526 0 0 0
4343
0x00007F99D34C6EE0 SCAN_RADIO 21 n/a 0 0 102 0 0 16 0 0 0 216808 220810 0 0 0
3900
0x00007F99D34C6EE0 SCAN_RADIO 20 n/a 0 1 68 0 0 0 0 0 0 518080 526974 0 0 0
8825
0x00007F99D34C6EE0 SCAN_RADIO 19 n/a 0 1 13962 0 0 310 310 0 0 427545 447655 0 0 0
6147
0x00007F99D34C6EE0 SCAN_RADIO 18 n/a 0 0 173 0 0 2 2 0 0 219850 223930 0 0 0
3907
0x00007F99D34C6EE0 SCAN_RADIO 17 n/a 0 0 39 0 0 6 6 0 0 243637 247319 0 0 0
3643
0x00007F99D34C6EE0 SCAN_RADIO 16 n/a 0 0 193 0 0 0 0 0 0 136991 139493 0 0 0
2309
0x00007F99D34C6EE0 SCAN_RADIO 15 n/a 0 0 364 0 0 128 128 0 0 134664 137137 0 0 0
2109
0x00007F99D34C6EE0 SCAN_RADIO 14 n/a 0 0 52 0 0 90 90 0 0 257142 261392 0 0 0
4198
0x00007F99D34C6EE0 SCAN_RADIO 13 n/a 0 0 214 0 0 118 118 0 0 179502 182811 0 0 0
3095
0x00007F99D34C6EE0 SCAN_RADIO 12 n/a 0 0 527 0 0 0 0 0 0 169237 172449 0 0 0
2685
0x00007F99D34C6EE0 SCAN_RADIO 11 n/a 0 1 54 0 0 0 0 0 0 438870 446363 0 0 0
7438
0x00007F99D34C6EE0 SCAN_RADIO 10 n/a 0 1 54 0 0 0 0 0 0 438871 446405 0 0 0
7479
0x00007F99D34C6EE0 SCAN_RADIO 9 n/a 0 0 507 0 0 0 0 0 0 167238 170397 0 0 0
2652
0x00007F99D34C6EE0 SCAN_RADIO 8 n/a 0 1 52 0 0 1 1 0 0 432856 440264 0 0 0
7355
0x00007F99D34C6EE0 SCAN_RADIO 7 n/a 0 0 191 0 0 4 4 0 0 175999 179221 0 0 0
3031
0x00007F99D34C6EE0 SCAN_RADIO 6 n/a 0 1 50 0 0 0 0 0 0 432808 440203 0 0 0
7344
0x00007F99D34C6EE0 SCAN_RADIO 5 n/a 0 0 38 0 0 1441 1398 0 0 244424 248014 0 0 0
3552
0x00007F99D34C6EE0 SCAN_RADIO 4 n/a 0 0 533 0 0 25 14 0 0 326689 332578 0 0 0
5356
0x00007F99D34C6EE0 SCAN_RADIO 3 n/a 0 0 1 0 0 2737 2737 0 0 133980 134785 0 0 0
804
0x00007F99D34C6EE0 SCAN_RADIO 2 n/a 0 1 292 0 0 25 25 0 0 399343 406545 0 0 0
6909
0x00007F99D34C6EE0 SCAN_RADIO 1 n/a 0 0 66704 0 0 517 500 0 0 26401 93604 0 0 0
499
0x00007F99D3AD61E0 SCAN_MANAGED 25 n/a 0 0 28 0 0 1431 1431 0 0 38589 39298 0 0
- 681
- Develop recommended action based on all above analysis and recommend indexes to be dropped to application developers. Get feedback from developers on indexes in question.
- Drop indexes and monitor post drop to ensure no negative impacts.
GOTO THE NEXT STATEMENT and REPEAT UNTIL Tuning Complete or return not beneficial.
