finding the performance bottlenecks in your application ian jones and roger schrag database...

Finding the Performance Bottlenecks in Your Application

Ian Jones and Roger Schrag

Database Specialists, Inc.

www.dbspecialists.com

IOUG-A Live! 1999

Paper #158

Finding the Bottleneck: Half the Battle in Tuning

• One bad SQL statement can spoil performance

• Too much code to take the “let’s tune every statement” approach

• DBA can’t be familiar with every line of code

Zero in on the Bottleneck

• Use the v$ views

• Use SQL Trace and timed statistics

• Use GUI tools

Today’s Presentation

• Half a dozen real-life examples– scenario– command-line efforts– resolution

• Demo of GUI tools– Enterprise Manager– freeware

The Terrifyingly Slow EDI Load• A transportation company used EDI to exchange data with

customers. They loaded EDI files into a temp table with SQL*Loader and then ran a 1500 line PL/SQL stored procedure to validate the data and update application tables.

• As more customers began sending EDI files, the PL/SQL stored procedure could no longer keep up. Data validation took as long as 24 hours for some EDI files.

• Where do we start tuning?

Start Load Process and Identify the Database SessionSQL> SELECT sid, serial#, status, username, osuser,

2 module, action

3 FROM v$session;

SID SERIAL# STATUS USERNAME OSUSER MODULE ACTION

---- ------- -------- -------- -------- -------- --------

1 1 ACTIVE oracle

2 1 ACTIVE oracle

3 1 ACTIVE oracle

4 1 ACTIVE oracle

5 1 ACTIVE oracle

6 1 ACTIVE oracle

7 54959 ACTIVE BJENKINS bjenkins de

8 4921 INACTIVE RTHOMAS rthomas de

9 2492 INACTIVE EJOHNSON ejohnson de

45 3415 ACTIVE EDI_LOAD edi SQL*Plus validate

View the Statement Being Executed

SQL> SELECT B.sql_text

2 FROM v$session A, v$sqlarea B

3 WHERE A.sid = 45

4 AND B.address = A.sql_address;

SQL_TEXT

-------------------------------------------------------

SELECT ITEM_ID FROM ITEM_TRANSLATIONS WHERE

SOURCE_ID = :b1 AND SUBSTR(SOURCE_SKU_CODE,1,6) = :b2

AND SYSDATE BETWEEN START_DATE_ACTIVE AND NVL

(END_DATE_ACTIVE, SYSDATE)

We Found a Bottleneck!PROCEDURE edi_validate_and_load

(p_cust_id IN NUMBER)

IS

CURSOR c_get_item_id (cp_cust_id IN NUMBER,

cp_sku IN VARCHAR2) IS

SELECT item_id

FROM item_translations

WHERE source_id = cp_cust_id

AND source_sku_code LIKE cp_sku || '%'

AND SYSDATE BETWEEN start_date_active

AND NVL (end_date_active, SYSDATE);

Disk Array Far Too Busy

• One third of a financial institution’s loan processing department started using a new PowerBuilder application. Response time was acceptable, but disk utilization on the server was at 100%.

• What could be done to reduce I/O so that the response time will still be acceptable after the rest of the department starts using the new application?

Identify the SQL Statements Causing the Most Disk Reads

SELECT sql_text, disk_reads, executions,

disk_reads / DECODE (executions, 0, 1, executions)

reads_per_exec

FROM v$sqlarea

ORDER BY reads_per_exec;

SELECT sql_text, disk_reads, executions,

disk_reads / DECODE (executions, 0, 1, executions)

reads_per_exec

FROM v$sqlarea

ORDER BY disk_reads;

SELECT sql_text, buffer_gets, executions,

buffer_gets / DECODE (executions, 0, 1, executions)

gets_per_exec

FROM v$sqlarea

ORDER BY buffer_gets;

Part of the Query Results…SQL_TEXT

------------------------------------------------------------

DISK_READS EXECUTIONS READS_PER_EXEC

---------- ---------- --------------

SELECT P.PRODUCT_DESC, CP.PRODUCT_ID, UPPER (:b1) CLIENT_ID

FROM CLIENT_PRODUCT CP, PRODUCT P WHERE CP.PRODUCT_ID =

P.PRODUCT_ID AND (UPPER (CP.CLIENT_ID),

CP.VALID_CLIENT_LEVEL_ID) IN (SELECT UPPER (:b1),

CA.VALID_CLIENT_LEVEL_ID FROM CLIENTS C, CLIENT_ADDRESS CA

WHERE UPPER (C.CLIENT_ID) = UPPER(:b1) AND C.CLIENT_ID

= CA.CLIENT_ID)

208734602 18657 11188.0046

The Same Query Formatted for Readability

SELECT P.product_desc, CP.product_id,

UPPER (:b1) client_id

FROM client_product CP, product P

WHERE CP.product_id = P.product_id

AND (UPPER (CP.client_id), CP.valid_client_level_id) IN

(SELECT UPPER (:b1), CA.valid_client_level_id

FROM clients C, client_address CA

WHERE UPPER (C.client_id) = UPPER(:b1)

AND C.client_id = CA.client_id)

A case-insensitive query turns out to be very inefficient. Now we know what to tune.

The So-Called “Locking Problem”

• A developer coded a PL/SQL function called compute_irr for computing internal rate of return. Response times varied widely. The developer claimed there was a locking problem on the database.

• What caused the slow performance in compute_irr?

SQL> SELECT sid, serial#, status, username, osuser,

2 module, action

3 FROM v$session;


---- ------- -------- -------- -------- -------- --------

1 1 ACTIVE oracle

2 1 ACTIVE oracle

3 1 ACTIVE oracle

4 1 ACTIVE oracle

5 1 ACTIVE oracle

6 1 ACTIVE oracle

9 2041 INACTIVE GL swatkins

10 4284 INACTIVE APPLSYS applmgr

62 7219 ACTIVE RSCHRAG rschrag SQL*Plus

63 7394 INACTIVE FA rschrag SQL*Plus

Start SQL*Plus and Identify the Database Session

Check Session Statistics Before Calling compute_irr

SQL> SELECT A.name, B.value

2 FROM v$statname A, v$sesstat B

3 WHERE B.statistic# IN (12, 37, 38, 39, 119, 123,

4 139, 140, 141)

5 AND B.sid = 63

6 AND A.statistic# = B.statistic#;

NAME VALUE

------------------------------ ----------

CPU used by this session 1292

db block gets 10186

consistent gets 86810

physical reads 346

table scans (long tables) 0

table scan rows gotten 1054

sorts (memory) 826

sorts (disk) 0

sorts (rows) 4693

Check Session Statistics Again While compute_irr Is Running




4 139, 140, 141)

5 AND B.sid = 63


NAME VALUE

------------------------------ ----------


db block gets 10294

consistent gets 86813

physical reads 346



sorts (memory) 826

sorts (disk) 0

sorts (rows) 4693

Session Statistic Before After 60Seconds

After 120Seconds

CPU Used by this session 1292 7274 13255db block gets 10186 10294 10294consistent gets 86810 86813 86813physical reads 346 346 346table scans (long tables) 0 0 0table scan rows gotten 1054 1054 1054sorts (memory) 826 826 826sorts (disk) 0 0 0sorts (rows) 4693 4693 4693

Compute the Deltas

Look for an infinite loop that involves no SQL statements.

Where Is the I/O Coming From?

• An application that performed well in a demo database quickly became I/O-bound when a significant amount of data was loaded into the database. It seemed as if there was a huge amount of I/O even with no users logged on to the application.

• What could be causing so much I/O activity?

Look at Physical Reads Instance-Wide and Per Session

SQL> SELECT name || ' (instance-wide)', value

2 FROM v$sysstat

3 WHERE statistic# = 39

4 UNION ALL

5 SELECT 'sid = ' || TO_CHAR (sid), value

6 FROM v$sesstat

7 WHERE statistic# = 39;

And the Results Are...NAME VALUE

-------------------------------- ----------

physical reads (instance-wide) 6048399

sid = 1 0

sid = 2 0

sid = 3 0

sid = 4 0

sid = 5 0

sid = 6 23120

sid = 7 186

sid = 8 0

sid = 9 18984

sid = 12 1375

sid = 13 5830219

sid = 17 27821

Investigate Suspicious Session 13SQL> SELECT sid, serial#, status, username, osuser,

2 module, action

3 FROM v$session

4 WHERE sid = 13;


---- ------- -------- --------- -------- -------- --------

13 829 ACTIVE APPSCHEMA daemon EXTRACT GET




4 139, 140, 141)

5 AND B.sid = 13


Suspicious Session 13 (continued)NAME VALUE

------------------------------ ----------


db block gets 5928722

consistent gets 293

physical reads 5873918



sorts (memory) 3

sorts (disk) 0

sorts (rows) 4210

What SQL Is Session 13 Executing?SQL> SELECT B.sql_text

2 FROM v$session A, v$sqlarea B

3 WHERE B.address = A.sql_address

4 AND A.sid = 13;

SQL_TEXT

------------------------------------------------------

SELECT * FROM TRANSACTIONS WHERE EXTRACTED = 'N’

Let me guess! The transactions table is about 10,000 blocks in size and the extracted column is not indexed.

“Fast” Reports That Were Too Slow

• A software vendor built an application using Oracle, Developer/2000, and a third-party reporting tool. A key report took about six seconds to complete, but consider that users will run the report in batches of several thousand.

• The report has thousands of lines of spaghetti code. How do you figure out what's slowing it down?

Build a Version of the Report That Enables SQL Trace

DECLARE

c INTEGER;

i INTEGER;

BEGIN

c := dbms_sql.open_cursor;

dbms_sql.parse (c,

'ALTER SESSION SET TIMED_STATISTICS=TRUE',

dbms_sql.native);

i := dbms_sql.execute (c);

dbms_sql.close_cursor (c);

dbms_session.set_sql_trace (TRUE);END;

Trace only what you need to trace!

Run the Report, Fetch the Trace File, Run TKPROF On It

OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS

call count cpu elapsed disk query

------- ------ -------- ---------- ---------- ----------

Parse 38 3.01 4.22 12 591

Execute 38 0.40 0.65 57 218

Fetch 41 0.57 0.77 91 294

------- ------ -------- ---------- ---------- ----------

total 117 3.98 5.64 160 1103

Misses in library cache during parse: 30

Look into using bind variables to reduce parsing.

The Chameleon Application

• An application ran well on a test database loaded with a full set of production data. But when the application was deployed in production, queries took over a minute to complete. In the test environment these same queries completed in under ten seconds.

• Policies forbid modifying code in production.

• What could be causing the application to run slower in production?

Find a Power User to Reproduce the Slow Behavior

• Identify the database session:

SQL> SELECT sid, serial#, status, username, osuser, 2 module, action

3 FROM v$session

4 WHERE username = 'MARYD';


---- ------- -------- --------- -------- -------- --------

17 9172 INACTIVE MARYD mbd frontend query

Enable Timed Statistics Temporarily

SQL> ALTER SYSTEM SET TIMED_STATISTICS = TRUE;

System altered.

SQL>

Enable SQl Trace Just Before the Query Is Launched

SQL> BEGIN

2 dbms_system.set_sql_trace_in_session (17, 9172, TRUE);

3 END;

4 /

PL/SQL procedure successfully completed.

SQL>

Disable SQL Trace When the Query Is Finished

SQL> BEGIN

2 dbms_system.set_sql_trace_in_session (17, 9172, FALSE);

3 END;

4 /

PL/SQL procedure successfully completed.

SQL>

SQL> ALTER SYSTEM SET TIMED_STATISTICS = FALSE;

System altered.

SQL>

Fetch the Trace File and Run TKPROFcall count cpu elapsed disk query current rows

------- ------ -------- ---------- ---------- ---------- ---------- ----------

Parse 1 1.44 1.45 0 0 0 0

Execute 1 0.00 0.00 0 0 0 0

Fetch 17 68.39 68.54 0 1878 2 254

------- ------ -------- ---------- ---------- ---------- ---------- ----------

total 19 69.83 69.99 0 1878 2 254

Misses in library cache during parse: 1

Optimizer goal: RULE

Parsing user id: 142 (BUILD4P2)

Rows Execution Plan

------- ---------------------------------------------------

0 SELECT STATEMENT GOAL: RULE

0 MERGE JOIN (OUTER)

254 SORT (JOIN)

115 NESTED LOOPS (OUTER)

253 NESTED LOOPS (OUTER)

254 TABLE ACCESS GOAL: ANALYZED (BY ROWID) OF 'MNME'

114539 INDEX GOAL: ANALYZED (FULL SCAN) OF 'MNME_I1'

(UNIQUE)

253 TABLE ACCESS GOAL: ANALYZED (BY ROWID) OF 'LCONTYPE'

254 INDEX GOAL: ANALYZED (UNIQUE SCAN) OF 'LCONTYPE_PK'

(UNIQUE)

115 TABLE ACCESS GOAL: ANALYZED (BY ROWID) OF 'MTAX'

254 INDEX GOAL: ANALYZED (UNIQUE SCAN) OF 'MTAX_I1'

(UNIQUE)

129 SORT (JOIN)

129 TABLE ACCESS GOAL: ANALYZED (FULL) OF 'LPOST’

The optimizer can behave differently from one Oracle version to the next.

GUI Tools Demo

To Find the Bottlenecks in Your Applications:

• Monitor v$sqlarea

• Monitor v$sysstat and v$sesstat

• Use SQL Trace judiciously

• Consider using GUI tools

ResourcesOracle Server Tuning

- Overview of the tuning process- How to use SQL Trace and TKPROF

Oracle Server Reference- Descriptions of all v$ views

High Performance SQL Tuning by Guy Harrison- Lots of tuning tips- Discussion of GUI tools available on the Internet

www.dbspecialists.com/present.html- Download this presentation- Download a companion white paper

Contact Information

Ian Jones: [email protected]

Roger Schrag: [email protected]

Database Specialists, Inc.

388 Market Street, Suite 400

San Francisco, CA 94111

415/344-0500

finding the performance bottlenecks in your application ian jones and roger schrag database...

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