1. 1 www.EvDBT.com Tuning PL/SQL procedures using DBMS_PROFILER 20-August 2009 Tim Gorman Evergreen Database Technologies, Inc. Northern California Oracle Users Group

2. 2 www.EvDBT.com Agenda Overview of tuning tools in Oracle –Tuning SQL –SQL Trace –TKPROF –Oracle Trace Analyzer –Method-R Profiler (www.method-r.com) –Tuning PL/SQL –DBMS_PROFILER –Log4plsql –???

3. 3 www.EvDBT.com Overview of performance tuning In order to improve anything, you have to measure it –Is it processing? –If so, what exactly is it doing? –Is it waiting on something? –If so, what exactly is it waiting for? Performance tuning is not an art, but a science –Instrumentation is key

4. 4 www.EvDBT.com Understanding where time is spent User Web server App server DB Server SQL*Net message from client (wait) CPU (service) db file sequential read (wait) Wait Event User Response Time Visual borrowed from Cary Millsap

5. 5 www.EvDBT.com Measuring time Tracing –Tracing is the recording of actions performed by a program, as they are performed Oracle SQL tracing –Event 10046 –alter session set events ‘10046 trace name context forever, level 8’ –exec dbms_support.start_trace –“Optimizing Oracle Performance” by Cary Millsap and Jeff Holt (O’Reilly & Associates, Sep 2003) –ISBN #059600527X

6. 6 www.EvDBT.com Summarizing tracing data Recording every action performed by a program generates huge volumes of data to analyze –Forest and trees –Look at the trees for diagnosing failures –Look at the forest to tune performance Application profiling –LOG4PLSQL on http://log4plsql.sourceforge.net/http://log4plsql.sourceforge.net/ –“C”/”C++” programs: UNIX “ prof ” utility –Java programs: EJP on http://www.sourceforge.nethttp://www.sourceforge.net –Commercial products from http://www.semdesigns.comhttp://www.semdesigns.com –profilers for Java, C#, C++, C, COBOL, other languages –TKPROF for SQL trace data –Method-R Profiler http://www.method-r.com/software/profiler-infohttp://www.method-r.com/software/profiler-info Profiling is the summarization of trace data

7. 7 www.EvDBT.com Profiling Using the UNIX “ prof ” utility as an example: –Compile a “C” program using the “-p” option to the “cc” compiler command –When compiled/linked program is executed, trace information is output to a file specified by $PROFDIR environment variable (default is “./mon.out”) –UNIX “ prof ” utility then reads trace information and produces a summarized “profile report” which summarizes: –Number of calls to functions –Amount of time spent in each function

8. 8 www.EvDBT.com Profiling SQL Trace is another example –SQL trace is enabled on a session –All SQL statements executed in that session dump trace information to a “.trc” file in USER_DUMP_DEST – TKPROF program simply reads information in the “.trc” file and summarizes it, displaying: –Execution counts –CPU and elapsed times –Number of physical, logical I/O –Number of rows fetched –Number of waits and time waited

9. 9 www.EvDBT.com What if the problem is not SQL? SQL statements perform work in the database –Summarizing SQL trace info is the best tool for tuning SQL What if the performance problem was in: –The network? Operating system? DB instance? –Database wait events can help –An application program, such as: –Java, C#, C++, C, COBOL, Fortran, Lisp? –PL/SQL?

10. 10 www.EvDBT.com DBMS_PROFILER Introduced with Oracle8i ( circa 1998 ) Not installed automatically –Some files in “ $ORACLE_HOME/rdbms/admin ” –Documented in MetaLink note #243755.1 –Download “ prof.zip ” from MetaLink –“Oracle PL/SQL Supplied Packages” reference on “DBMS_PROFILER” Generates trace data in PL/SQL programs –Trace data saved to tables in database –SQL*Plus script produces summarized “profile report” as HTML

11. 11 www.EvDBT.com DBMS_PROFILER Files found in “$ORACLE_HOME/rdbms/admin” SQL*Plus script “profload.sql” creates the package DBMS_PROFILER –Run once for global setup on database –Must be performed by SYS user –Also validates package after creation SQL*Plus script “proftab.sql” creates tables to store trace data –Create private sets of tables for each user –Each user has the three tables and single sequence –Create a “global set” of tables for all users –DBA is responsible for granting appropriate permissions and creating synonyms for the three tables and the single sequence

12. 12 www.EvDBT.com DBMS_PROFILER Important extra files provided in “prof.zip” –SQL*Plus script “profiler.sql” –Queries data generated by runs of the DBMS_PROFILER package –Generates HTML profiler report as output –SQL*Plus script “profgsrc.sql” –Extracts the source of a stored package, procedure, or function to an ASCII text file for editing –So that DBMS_PROFILER procedures can be added to that source code…

13. 13 www.EvDBT.com Using DBMS_PROFILER Initial setup: –DBMS_PROFILER package has been created by the DBA using “profload.sql”… –developer/user has created the tables using “proftab.sql” Add profiler procedures to PL/SQL source –Procedure START_PROFILER(‘run-comment’) –Procedure STOP_PROFILER Recompile and run the procedure

14. 14 www.EvDBT.com Using DBMS_PROFILER After running an instrumented PL/SQL program: –Execute the SQL*Plus script “profiler.sql” –It will display each session’s RUN-ID, a timestamp, and the RUN-COMMENT –Choose the appropriate RUN-ID –Produces spooled output to a file named “profiler_.html”

15. 15 www.EvDBT.com Case Study #1 A PL/SQL procedure named PROFTEST1 –It queries data from a table –Stores the data in a comma-separated string –Then, repeatedly parses and displays each item in the string There are (at least) two ways to call the INSTR() function here: –instr(string, ‘,’, 1, n) –instr(string, ‘,’, x, 1) –Which is faster??? Is there a difference?

16. 16 www.EvDBT.com Case Study #1 Files: –proftest1.sql –DDL to create stored procedure and table –Including use of DBMS_PROFILER –run_proftest1.sql –SQL*Plus script to run the test –proftest1.tkp –Output from tkprof sort=prsela,exeela,fchela explain= / –proftest1_19.html –proftest1_20.html

17. 17 www.EvDBT.com Case Study #1 No real surprise when you think about it –Using this is faster… –instr(string, pattern,, 1) –…than… –instr(string, pattern, 1, )” –…but THAT MUCH FASTER??? An easy mistake to make? –Everything seems obvious in hindsight…

18. 18 www.EvDBT.com Case Study #2 Script to estimate the number of rows per block –Originally written for Oracle v6 –Adapted to Oracle7 without modification –New ROWID formats in v8+ forced changes to the script Started using DBMS_ROWID package in query when Oracle8 ROWIDs came on the scene –Extremely slow –Went back to using SUBSTR on ROWID strings

19. 19 www.EvDBT.com Case Study #2 Files: –proftest2.sql –DDL to create stored procedure and table –Including use of DBMS_SUPPORT and DBMS_PROFILER –run_proftest2.sql –SQL*Plus script to run the test –proftest2.tkp –Output from tkprof sort=prsela,exeela,fchela explain= / –proftest2_1.html –proftest2_2.html

20. 20 www.EvDBT.com Case Study #2 DBMS_PROFILER is not recursive –PL/SQL modules called within instrumented procedures are not traced… –PL/SQL modules called within SQL statements are not traced… –…unless they themselves are instrumented with START/STOP_PROFILER calls… The resolution of replacing DBMS_ROWID package calls with SUBSTR was easily determined using SQL Trace and TKPROF –But DBMS_PROFILER pinpointed the exact cause –Replacing DBMS_ROWID with SUBSTR was just a guess with SQL tracing…

21. 21 www.EvDBT.com Q & A? Questions? Comments? URL: http://www.EvDBT.comhttp://www.EvDBT.com Email: Tim@EvDBT.comTim@EvDBT.com