SQL Tuning for Expert DBAs - PDF Free Download

SQL Tuning for Expert DBAs GP (Gongloor Prabhaker) Senior Director of Product Management Oracle Management Cloud, Oracle Corporation Konstantin Kerekovski, DBA, Raymond James Financial Inc. Oct 03, 2017 Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted

Safe Harbor Statement The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle s products remains at the sole discretion of Oracle. Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 3

Program Agenda 1 2 3 4 SQL Tuning: Challenges and existing solutions Proactive approach and tips Reactive approach and tips Customer Case study Please visit us at Demo Grounds: Moscone West, SOA-052, Database Monitoring and Performance Management with Oracle Enterprise Manager Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 4

Program Agenda 1 2 3 4 SQL Tuning: Challenges and existing solutions Proactive approach and tips Reactive approach and tips Customer Case study Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 6

SQL Tuning: Why is guess work involved? Optimizer Related Resource Contention Application Specific Issues Lack of Automated, E2E and scalable solution End-user Expertise Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 7

SQL Performance Issues: Broad categories Optimizer Related Stale/Missing statistics Incomplete statistics Improper optimizer configuration Upgraded Database: new optimizer Rapidly changing data Resource Related Hardware resource crunch Contention (row lock/ block contention) Not parallelized (no scaling to large data) Improperly parallelized (partially parallelized, skews) Application Issues Missing access structures Poorly written SQL statements Bind-sensitive SQL with bind peeking (Cursor Sharing) Literal usage Lack of SQL & Optimizer Expertise Limited knowledge of SQL and Optimizer Tunes individual or few statements vs. entire workload Lack of Automation Manual effort, time consuming Lack of scalability with high volume SQL (100K) Unintuitive techniques and point solutions Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 8

SQL Tuning: Existing solutions How DBAs tune SQL today? Use SQL Trace to identify offending SQL solution Prohibitive on production Disable index access by modifying predicates (to_char, to_number) Change init.ora parameters (optimizer_..) Adding indexes Most apps are already over-indexed Materialized Views Partitioning, etc. Existing solutions have severe limitations, are not scalable and mostly reactive in nature, use trial and error methodology Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 9

Proactive Approach Become the Proactive DBA using Oracle s rich tool set! A DBA has Oracle s rich tool set available to identify problems and remediate problems before they happen in production. Proactive DBA should use the following tools: ADDM to detect systemic problems and remediate them by following ADDM recommendations* Automatic SQL Tuning advisor to tune high load SQL statements over time it is available out of the box* SQL Access Advisor to make sure your application has optimal access structures (indexes and type, MVs, MV logs, etc.) and partitioning scheme, tune entire workload* SPA Quick in production environments to quickly assess impact of routine system changes (for e.g., SQL Profile validation, optimizer related changes, optimizer refresh statistics) without impacting production* SPA to validate system changes such as migration to Oracle Database Cloud, Exadata Cloud Machine, etc.* *OOW 2016: Eliminating Guesswork from SQL Tuning [CON6975] Copyright 2017, Oracle and/or its affiliates. All rights reserved. 12

SQL Performance Analyzer Helps users predict the impact of system changes on SQL workload Low overhead capture of SQL workload to SQL Tuning Set (STS) on production system Build different SQL trials (experiments) of SQL statements performance by test execution or explain plan Integrated with STS, SQL Plan Baselines, & SQL Tuning Advisor to form an end-to-end solution SQL Plans + Statistics Pre-change Trial Compare SQL Performance SQL Plans + Statistics Post-change Trial Analysis Report Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 13

DBCS Migration Use Case As a DBA, you have been tasked by management to migrate your 11.2 database to the latest Cloud DB release. At the same time, the requirement is to make sure the performance is same or better than before, how can I accomplish this? Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 14

Validate Cloud Migration with SPA On-Premise Oracle Cloud Step3a: Conduct SPA trials SPA Task Trial 1: Build (Convert) from STS Trial 2: Test Execute or Explain Plan Step 1: Capture representative workload to STS Step 2: Clone On-premise database to Cloud Step 3b: Generate SPA Report and fix regressions Analysis Report Copyright 2017, Oracle and/or its affiliates. All rights reserved. 15

SPA - Concurrent SQL Execution New in 18.1 SPA trials are currently executed serially one statement at a time When SQL Tuning Sets contain a large number of statements, the trial could take significant time. For example, EBS suite may have 1 million unique SQL statements Under utilized server if using large system Concurrent SQL execution within a SPA trial reduces duration to complete the trial, therefore reduces testing time User specifies degree of parallelism with SPA parameter TEST_EXECUTE_DOP For example, a SQL Tuning Set with 125,000 statements reduced testing from 12.5 hours to 2 hours with a degree of parallelism of 8 Tip: Use SPA concurrent SQL execution in test environment for STS with a large number (thousands or higher) of SQL statements Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 18

SPA Result Set Validation New in 18.1 Result set validation required for certain environments e.g. government drug research trials, pharma industries, etc. An additional assurance that SQL produces correct results with new environment / software SPA report can be generated for before and after change trials comparing whether identical result sets were produced SPA result set validation enabled with SPA parameter COMPARE_RESULTSET (defaults to true) Tip: Run before and after trials with exact same dataset for result set validation If result sets differ with same input dataset contact Oracle Support Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 19

Program Agenda 1 2 3 4 SQL Tuning: Challenges and existing solutions Proactive Approach and tips Reactive Approach and tips Customer Case study Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 21

SQL Tuning Tips - Reactive Approach Proactive SQL Tuning should resolve most of your day-to-day issues, however sometimes reactive tuning is needed DBA should use the following tools for reactive SQL Tuning: ASH Analytics for transient performance analysis and drilling down on SQL dimensions (by execution plan operation, SQL_ID, PDB, Action, Module, etc.) SQL Monitor for complex run-time execution statistics on long running or Parallel executions such as which plan operation line that consumes resources such as CPU and I/O, overall PGA usage and Parallel distribution SQL Tuning Advisor getting comprehensive analysis and recommendations on problematic SQL statements such as profiles, statistics and new access structure Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 22

Tip: Use Real-Time SQL Monitoring For Detailed Execution Statistics On Long Running Or Parallel Executions Looking inside the SQL Enabled out-of-the-box with no performance impact Automatically monitors SQL executions that: Consume more than 5 seconds of CPU or I/O time Are running parallel: PQ, PDML, PDDL Monitors each execution independently Exposes monitoring statistics at multiple levels Global execution level Plan operation level (Plan Tuning) Parallel Execution level (PX Tuning) Guides your tuning efforts SQL level metrics CPU, I/O requests, throughput, PGA, temp space Graphical explain plan I/O statistics for each operation Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 23

Real-Time SQL Monitoring Looking inside the SQL Can also be accessed via ASH Analytics -> Select an SQL ID -> Select SQL Monitor from Detail section. Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 26

Real-Time SQL Monitoring Use cases Case Study 1 Adaptive Plans Case Study 2 Long Execution plan Case Study 3 PL/SQL Monitoring Case Study 4 Poor indexing Case Study 5 Parallel Execution Downgrade Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 27

Real-time SQL Monitoring with Adaptive Plans Generate script for problem SQL with binds and execute (6 min) Copyright 2016, Oracle and/or its affiliates. All rights reserved. Oracle Confidential Internal 29

SQL Monitoring Case Study 1 Case Study 1: Adaptive Plans How can I determine if a query has self tuned with the adaptive plan feature? Can I identify the values of my bind variables? Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 30

SQL Monitoring Use Cases Case Study 2: Analyzing Large SQL Execution Plans Comprehensive view of execution plan Easy to pinpoint operations and objects that consume the most resources Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 32

SQL Monitoring Use Cases Case Study 2: Analyzing Large SQL Execution Plans Q: I have a complex query with a complex query plan, how can I identify which operations and objects consume the most resources? SELECT /*+ MONITOR */ avg(ss_quantity),avg(ss_ext_sales_price),avg(ss_ext_wholesale_cost),sum(ss_ext_wholesale_cost) from store_sales,store,customer_demographics,household_demographics,customer_address,date_dim where s_store_sk = ss_store_sk and ss_sold_date_sk = d_date_sk and d_year = 2001 and ( (ss_hdemo_sk=hd_demo_sk and cd_demo_sk = ss_cdemo_sk and cd_marital_status = 'M and cd_education_status = '4 yr Degree and ss_sales_price between 100.00 and 150.00 and hd_dep_count = 3 ) or (ss_hdemo_sk=hd_demo_sk and cd_demo_sk = ss_cdemo_sk and cd_marital_status = 'D and cd_education_status = 'Primary' and ss_sales_price between 50.00 and 100.00 and hd_dep_count = 1 ) or (ss_hdemo_sk=hd_demo_sk and cd_demo_sk = ss_cdemo_sk and cd_marital_status = 'U and cd_education_status = 'Advanced Degree and ss_sales_price between 150.00 and 200.00 and hd_dep_count = 1 ) ) and( (ss_addr_sk = ca_address_sk and ca_country = 'United States and ca_state in ('KY', 'GA', 'NM') and ss_net_profit between 100 and 200 ) or (ss_addr_sk = ca_address_sk and ca_country = 'United States and ca_state in ('MT', 'OR', 'IN') and ss_net_profit between 150 and 300 ) or (ss_addr_sk = ca_address_sk and ca_country = 'United States and ca_state in ('WI', 'MO', 'WV') and ss_net_profit between 50 and 250 ) ) Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 33

SQL Monitoring Use Cases Case Study 2: Analyzing Large SQL Execution Plans Q: I have a complex query with a complex query plan, how can I identify which operations and objects consume the most resources? Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 34

SQL Monitoring Use Cases Case Study 2: Analyzing Large SQL Execution Plans Q: I have a complex query with a complex query plan, how can I identify which operations and objects consume the most resources? Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 35

SQL Monitoring Use Cases Case Study 2: Analyzing Large SQL Execution Plans Q: I have a complex query with a complex query plan, how can I identify which operations and objects consume the most resources? Solution: All activity is against STORE_SALES. Consider partitioning the table. Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 36

SQL Monitoring Use Cases Real-Time PL/SQL Monitoring PL/SQL execution no longer a black box Answers questions like why did my DBMS_STATS job take twice as long this time? Shows global (PL/SQL) and SQL level statistics Each SQL called by PL/SQL recursively monitored Drill-down to slow SQL for diagnosing unexpected PL/SQL behavior Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 37

SQL Monitoring Use Cases Case Study 3: Real-Time PL/SQL Monitoring Q: I have a PL/SQL procedure that takes a long time, can I identify which SQL statement that is my largest resource consumer? Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 38

SQL Monitoring Use Cases Case Study 3: Real-Time PL/SQL Monitoring Q: I have a PL/SQL procedure that takes a long time, can I identify which SQL statement that is my largest resource consumer? Highest CPU usage Most elapsed time Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 40

SQL Monitoring Use Cases Case Study 4: Poor Indexing Q: I have added many indexes to my database. I still have several queries with bad performance. Can I determine if my indexes are used efficiently? Initial Query Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 45

SQL Monitoring Use Cases Case Study 4: Poor Indexing Q:I have added a large amount of indexes to my database. I still have several queries with bad performance. Can I identify that my indexes are used efficient? Initial Query Tuned Query Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 46

SQL Monitoring Use Cases Case Study 4: Poor Indexing Q: I have added many indexes to my database. I still have several queries with bad performance. Can I determine if my indexes are used efficiently? Initial Query Tuned Query Tuned Query / Cached Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 47

SQL Monitoring Use Cases Case Study 5: Parallel Execution Downgrade Query requests parallel degree 4. Why is it downgraded to parallel degree 2? Copyright 2017, Oracle and/or its affiliates. All rights reserved.

SQL Monitoring Use Cases Case Study 5: Parallel Execution Downgrade Query requests parallel degree 4. Why is it downgraded to parallel degree 2? select qksxareasons,indx from x$qksxa_reason where qksxareasons like '%DOP downgrade% ; QKSXAREASONS INDX ------------------------------------------------------------ ---------- DOP downgrade due to adaptive DOP 351 DOP downgrade due to resource manager max DOP 352 DOP downgrade due to insufficient number of processes 353 DOP downgrade because slaves failed to join 354 Copyright 2017, Oracle and/or its affiliates. All rights reserved.

SQL Monitoring Use Cases Case Study 5: Parallel Execution Downgrade Query requests parallel degree 4. Why is it downgraded to parallel degree 2? Solution: Consider changing the maximum DOP on Resource Consumer Group Copyright 2017, Oracle and/or its affiliates. All rights reserved.

SQL Tuning Advisor Exadata Enhancement NEW IN 18.1 SQL Tuning Advisor detects if SQL is executing on Exadata SQL Tuning Advisor privately gathers system statistics and does analysis with and without these statistics If a better execution plan is found with these system statistics, an Exadata-aware SQL Profile is recommended Can result in 10x or better performance improvement for SQLs which can benefit from Exadata hardware - e.g. cell smart scans Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 53

SQL Tuning Advisor Exadata Enhancement Without Exadata aware SQL Profile 1.9 minutes: NEW IN 18.1 With-Exadata aware SQL Profile 13 seconds: Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 54

57 RAYMOND JAMES FINANCIAL HTTPS://WWW.RAYMONDJAMES.COM/

KONSTANTIN KEREKOVSKI Work Experience: American Express Senior Oracle DBA, 11g, 12c, RAC, GG, ADG Raymond James Senior Oracle DBA, 11g, 12c, Exadata, ODA, RAC, GG, ADG LinkedIn: www.linkedin.com/in/konstantin-kerekovski-34740071 Speaker: IOUG Collaborate 2017 SOUG (Suncoast Oracle User Group) NYOUG (New York Oracle User Group) 58

THE PROBLEM Production Oracle Data Integrator (ODI) jobs are running slowly due to suboptimal execution plans on INSERT INTO XYZ SELECT. queries. The INSERT queries cannot be readily altered due to declarative nature of ODI and internal Change Management process. The business is being impacted because multiple other ETL and batch jobs depend on the completion of ODI jobs. 59

PROBLEM IDENTIFICATION The problem was clearly evident in the Top Activity page of OEM for the database in question. 60

61 THE SOLUTION SQL TUNING ADVISOR

62 PLAN COMPARISON

IMPLEMENTATION The implementation of the SQL Profiles and/or statistics gathering is as simple as following the guided instructions from the OEM SQL Tuning recommendations screen. 63

TOP ACTIVITY BEFORE TUNING TOP ACTIVITY AFTER TUNING 64

THE IMPACT OF SQL TUNING ADVISOR The long running ODI job s runtime improved dramatically. No development effort was necessary, thus saving money on labor costs on tuning efforts and regression testing efforts. The change was easily implementable and because SQL Profiles can easily be disabled, the change can be backed out if any issues arise. The change can be easily propagated throughout the entire SDLC due to the portable nature of SQL Profiles. Business processes which depend on ODI jobs to complete were no longer impacted and completed ahead of schedule. 65

What is it? TIP SHOULD I USE SQL BASELINES OR SQL PROFILES? SQL BASELINE - A set of stored, approved execution plans for a given SQL statement that are used instead of plans obtained during normal hard parsing. When do I use it? - During Database Upgrades for the purpose of avoiding performance regression due to new optimizer features ( E.G. Adaptive Plans in 12.1), missing statistics, etc. - When you only want one specific execution plan to be used. What is it? SQL PROFILE - Extra information to be used by the optimizer during parsing. When do I use it? - When you just want to help the optimizer with extra information without dictating a specific execution plan. - When SQL Execution Plans are unstable and changing adversely due to issues such as inaccurate/stale Optimizer Statistics, bind variable peeking, etc. 66

SQL Tuning for Expert DBAs: Summary Become the proactive DBA, use: ADDM to detect systemic problems and remediate them by following ADDM recommendations Automatic SQL Tuning Advisor to tune high load SQL statements over time SQL Access Advisor to assure that your application has optimal access structures (indexes and type, MVs, MV logs, etc.). Tunes the entire workload SPA Quick Check in production environments to quickly assess impact of routine system changes (for e.g., optimizer refresh statistics) SPA to validate system changes such as migration to Oracle Database Cloud, Exadata Cloud Machine, etc. If you have to perform reactive SQL tuning, use: ASH Analytics to identify your top resource consumers SQL Monitor for detailed execution statistics on long running or parallel executions SQL Tuning Advisor to identify and remediate: Stale statistics Incorrect cardinality estimations Data correlations Copyright 2017, Oracle and/or its affiliates. All rights reserved. Confidential Oracle Internal/Restricted/Highly Restricted 67