Top Tips for Improving Database Performance - RainFocus · Oracle Database Performance Tuning...

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Top Tips for Improving Database Performance

Kurt EngeleiterPrincipal Product ManagerOracle

Venkata Ravi Kumar YenugulaLead Oracle DBARaymond James

Confidential – Oracle Internal/Restricted/Highly Restricted


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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.

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Program Agenda

Introduction

Oracle Database Performance Tuning Fundamentals

Performance Tuning Tips

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Oracle Confidential – Internal/Restricted/Highly Restricted 3


Program Agenda

Introduction



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Top Challenges: Database Management

52% Rapid diagnoses of database

performance problems

45% Identifying application (SQL)

issues

37% Validating and applying SQL

tuning solutions

Key Takeaway: Improve & Ensure Higher Quality of Service

?

Source: THE RAPIDLY ACCELERATING CLOUD-ENABLED ENTERPRISE: 2015 IOUG Survey On Database Manageability


What can cause database performance to change?



Environment Changes That Affect Performance

• Data growth

• User population growth

• Infrastructure changes

– Server upgrades

– Changes in size or type of disk storage

–Migration to new platforms including migration to Cloud

• Database Consolidation

7Oracle Confidential – Internal


DBA Actions That Affect Performance

• Adding or dropping indexes, partitioning tables, adding materialized views

• Gathering optimizer statistics

• Modifying init.ora parameters

• Implementing new features such as Compression, Database In-Memory

• Applying patches – one offs, patch bundles

• Version upgrades or patchsets

8Oracle Confidential – Internal


Program Agenda

Introduction



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Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Confidential – Oracle Internal/Restricted/Highly Restricted 10

DB Time

• Total time in database calls by foreground sessions

• Includes

– CPU time

– IO time

– Active wait (non-idle wait) time

• Basic unit for Oracle performance analysis

CPU

I/O

Wait

DB Time


Quiz

True or False:

The maximum DB Time a four CPU system can accumulate in one hour is four hours of DB Time.


In addition to using CPU, and doing I/O, one or many database sessions could be in non-idle wait for that one hour. Each of those sessions would be accumulating DB Time. The database could accumulate much more than four hours of DB Time in one hour.

Answer: FALSE

Copyright © 2017, Oracle and/or its affiliates. All rights reserved. | Oracle Confidential – Internal/Restricted/Highly Restricted 13

Colored Areas in EM = DB Time

• Active Sessions by wait class over time

• More DB time, more tuning opportunities

• DB time increases as system load increases

• DB time increases as system performance degrades.


DB Time in AWR Report

• Top 10 events in AWR report are reported in order of DB Time, descending

• TIP: To improve database performance, focus on:

• Reducing the highest DB Time events which can be done with the least effort


Program Agenda

Introduction



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Tips on Reading an AWR Report



Tips On Reading An AWR Report

• Tip:

– Check operating system level first – verify not maxed out on CPU

– DB Time is inflated when CPU bound


Db file sequential read

Run-queue

On CPU Db file sequential read

Run-queue

On CPU

User 1

Actual wait time Actual wait time

Recorded wait time Recorded wait time



• For a basic understanding of the database and environment – check the top of the report:– DB Time vs elapsed time, –Number of CPUs and cores – Amount of memory– Number of database sessions




• Read the ADDM findings at the top of the report – ADDM report automatically included starting with database 12

• Look at the full ADDM report at the end of the AWR report• Identifies top DB Time targets for tuning• Tip: ADDM specifies subsystems that are not a problem, e.g. network, interconnect




• Look at 10 top timed events section, focus on highest DB Time that can be reduced with least effort




• Review top SQL sections based on top 10 events. Identify top SQL candidates for tuning:

– If CPU is a top event, look at top SQL by CPU section

– If I/O is a top event, look at top SQL by I/O section

– If wait events are top events, look at SQL by elapsed time section

– Frequently the same SQL will show up in one or more of these sections




• Review the database parameters section

• Tip: Best practice is to have as few non-default database parameters set as possible

–Minimizing non-default parameters means will execute most common code path –most optimized, fewest potential issues

– Underscore parameters particularly suspect


x


Database Performance Hub

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Holistic Performance Management

• Single view of DB performance

– ADDM, SQL Tuning, Real-Time SQL Monitoring, ASH Analytics

• Switch between ASH analytics, workload view, ADDM findings and SQL monitoring seamlessly

• Supports both real-time & historical mode

• Historical view of SQL Monitoring reports


Tip: How to Generate Performance Hub Report

• Performance Hub report generated from SQL*Plus:

– @$ORACLE_HOME/rdbms/admin/perfhubrpt.sql

OR calling dbms_perf.report_perfhub(….) function

• Performance Hub appended to AWR report:

– @$ORACLE_HOME/rdbms/admin/awrrpt.sql

– Choose ‘active-html’ report

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DemoPerfhub Report



Tips on Assuring Performance During Routine System Changes



• Helps users predict the impact of routine system changes on production SQL workload

• Low overhead capture of SQL workload to SQL Tuning Set (STS)

• Build different SQL trials (experiments) of SQL statements performance by test execution or explain plan

• Day to day use cases integrated with SPA Quick Check, SQL Plan Baselines, & SQL Tuning Advisor to form an end-to-end solution


Proactive Performance Management: SPA Quick Check

Analysis Report

Compare SQLPerformance

Post-change TrialPre-change Trial

SQL Plans + Statistics SQL Plans + Statistics


• Optimized– Optimized for use on prod systems

– Optimal Trial or Explain Plan mode

– Disable multi-executions, full DML execute disabled

• Controlled– Per SQL time limits

– Testing scoped to private session

– Associate with Resource Consumer Group

• Change-Aware– Context-aware change testing workflows, such as,

– Optimizer gather statistics

– Init.ora parameter changes


Proactive Performance ManagementPredict the impact of routine system changes on SQL workload response time

SPA Quick Check

Production Database

OptimizedControlled/Sc

oped

Change-Aware

Optimal Trial

Mode, no DML

execute

Pre-selected

STS and

default SPA

settings

Per SQL Time Limits,

Limits testing scope to

private session

Context-aware

change testing

DBA


Proactive Performance Management


Predict the impact of system changes on SQL workload response time

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DemoSQL Performance Analyzer



SPA - Concurrent SQL Execution

• SPA trials are currently executed serially one statement at a time

– This can lead to long tests when SQL Tuning Sets contain a large number of statements. For example, EBS suite may have 1 million unique SQL statements

• 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


New in

18.1


SPA – Result Set Validation

• Result set validation required for certain environments – e.g. government drug research trials, pharma industries, etc. An additional assurance 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

• 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


New in

18.1


Tips on SQL Tuning and Exadata



Reactive Performance Management


How to go about tuning the sub-optimal SQL?

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Statistics Analysis

SQL Profiling

Access Path Analysis

SQL Restructure Analysis

Alternative Plan Analysis

Parallel Query Analysis

Automatic Tuning Optimizer

Administrator

Comprehensive SQL Tuning Recommendations

Gather Missing or Stale Statistics

Create a SQL Profile

Add Missing Access Structures

Modify SQL Constructs

Adopt Alternative

Execution Plan

Create Parallel SQL Profile

SQL Tuning Advisor

• Gives recommendations on various problems found during analysis phase

• Uses the same CBO but has more time budget for comprehensive analysis

• Identifies alternate execution plans using real time and historical performance data

• Recommends SQL profile to compensate for incorrect statistics and transparently improve performance


Tip: SQL Tuning Advisor – Choose Highest DB Time, Most Targeted Improvement Recommendation

• SQL Tuning Advisor provides DB Time improvement benefits for its recommendations

• Choose the highest DB Time, most targeted recommendation

• SQL Profile affects single statement

• Index could affect entire workload – requires additional validation (SQL Access Advisor)


SQL Tuning Advisor Exadata Enhancement

• 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 will be recommended

• Can result in 10x or better performance improvement for SQLs which can benefit from Exadata hardware - e.g. cell smart scans


NEW IN

18.1


SQL Tuning Advisor Exadata Enhancement


NEW IN

18.1

Without Exadata aware SQL Profile – 1.9 minutes:

With Exadata aware SQL Profile – 13 seconds:


Tips on Tuning Active Data Guard



AWR Support for Remote Snapshots and ADG

• Problem

– AWR snapshots cannot be taken in a read-only standby environment

– Performance monitoring and analysis is limited to basic STATSPACK functionality

• Solution– In Oracle Database 12.2, AWR framework enhanced to support capture of remote

snapshots from any generic database including Active Data Guard (ADG) databases. • A target catalog database collects snapshots from the remote databases (sources)

• Snapshots can be collected automatically or manually

• AWR tables on the catalog database accumulate snapshot data from all sources via database links

• Source databases must be registered on the catalog via new DBMS_WORKLOAD_REPOSITORY.REGISTER_REMOTE_DATABASE API



Remote Snapshot Configuration for ADG Database


Primary

Local AWR Data

Catalog database

Remote AWR Data

ADG Reader Farm

Source databases

Active Data Guard 3. Define the source databases

4. Define the target database

5. Create the topology

6. Register the source databases

7. Register the source databases for AWR service


SQL Tuning Advisor Support for Active Data Guard

• Problem

– ADG databases are widely used to offload reporting or ad hoc query-only jobs from primary

– Reporting workload profile is different from primary and often requires tuning

• Solution• Oracle Database 12.2 introduces the ability to tune SQLs workloads running on ADG database

• All SQL Tuning Advisor tasks issued at the standby

– Create tuning task, execute tuning task and implement SQL Profile recommendations can be run on standby

– Test execution (heavy lifting) happens on standby, only minimal write related activity on primary

• The required data for the above tasks are fetched from primary over a database link from standby

• Task details and tuning results are stored at primary and the essential data required to construct the report is accessed remotely from primary

• The report is constructed locally at the standby, with no CPU overhead in primary



SQL Tuning Advisor Support for Active Data Guard

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Primary Standby

dblink_to_primary

create tuning taskexecute tuning taskreport tuning taskimplement recommendations

– All changes are done on primary and propagated from primary to standby by redo apply

– Support for PDB level tuning

– The tuning task is executed at the standby, with no CPU overhead in primary


Tips on Troubleshooting a Hung Database





Diagnose persistent performance issues

Real-Time ADDM

ComparePeriod ADDMADDM

Enhanced Real-Time

ADDM

• Diagnose persistent performance issues

• Analyzes AWR snapshots

• Regular interval

• Automatic / Manual

• In-depth performance comparison across two periods

• Relies on AWR data

• Manual

• Hung or extremely slow databases

• Uses a normal and diagnostic mode connection

• Manual

• Proactively detect & diagnose transient high-impact problems

• Built inside the DB

• Automatically runs every 3 seconds


• My database is unresponsive and end-users are complaining of performance issues. Should I bounce the database or wait for some time for problem to go away?

• Database Hung state

- Blocking Sessions

- Memory allocation issues

- Library cache issues

- Unresponsive Storage (ASM)

- Interconnect problems






Tip: Diagnose hung database issues using Real-Time ADDM

• Identify the problem area

• Turns out to be a SQL that consumes significant amount of DB Time

• Review SQL Monitor report of the problem SQL for in-depth analysis




Tip: Diagnose Hung database issues using Real-Time ADDM

• Refer back to Real-Time ADDM to nail this down as login storm issue, understand more about this query


Summary

• To improve database performance, reduce DB Time

• Use automated tools such as SQL Performance Analyzer and SQL Tuning Advisor to maximize productivity

• Use Real-Time ADDM to troubleshoot hung databases

• Use AWR and Perfhub for in-depth performance analysis


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RAVI KUMAR YV

Performance Active Hub Report – Oracle Exadata x6 (HR)

Performance Hub active report shows Load Profile, Active Sessions, Host CPU and IO


Performance Hub active report shows CELL CPU, Read/Write Latency and IO Requests


Performance Hub active report shows Instance-wise Resources Utilization


Performance Hub active report enables you CELL Level Statistics (Flash Cache and IO bytes)

SQL Performance Analyzer Task Report – Buffer Gets

Change-aware: Knows what change is being tested.

Intelligently limits impact to private test session.

SQL Performance Analyzer Task Report – Elapsed Time

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

SQL Performance Analyzer Task Report – Buffer Gets

After Implementation through SPA – SQL ID ‘74cpnuu24wmx7'

https://dugong1.rjf.com:7803/em/console/database/instance/globalAwrDiffReport?event=viewReport&target=cdssfqa.rjf.com&type=rac_database&_em.coIFR=true#74cpnuu24wmx7

SQL Performance Analyzer Task Report – Elapsed Time

After Implementation through SPA – SQL ID ‘74cpnuu24wmx7'

https://dugong1.rjf.com:7803/em/console/database/instance/globalAwrDiffReport?event=viewReport&target=cdssfqa.rjf.com&type=rac_database&_em.coIFR=true#74cpnuu24wmx7

EXAFUSION PARAMETER

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Exafusion is Direct-to-Wire protocol allows database processes to read

and send Oracle RAC messages directly over the Infiniband network

bypassing the overhead of entering the OS kernel, and running the

normal networking software stack.

This improves the response time and scalability of the Oracle RAC

environment on Oracle Exadata. Data is transferred directly from user

space to the Infiniband network, leading to reduced CPU utilization

and better scale-out performance.

PRE-REQUISITES FOR EXAFUSION

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Pre-Requisites for Exafusion

Oracle Exadata Storage Server Software release 12.1.2.1.1 or later.

Oracle Database software Release 12.1.0.2.0 BP11 or later.

Oracle Enterprise Kernel 2 Quarterly Update 5 (UEK2QU5) kernels (2.6.39-400.2nn).

Enable ‘Exafusion’ Parameter

Exafusion is disabled by default.

To enable Exafusion, set the EXAFUSION_ENABLED initialization parameter to 1.

To disable Exafusion, set the EXAFUSION_ENABLED initialization parameter to 0.

This parameter cannot be set dynamically. It must be set before instance startup.

All of the instances in an Oracle RAC cluster must enable this parameter, or all of the instances in

an Oracle RAC cluster must disable the parameter.

Improved Response Time and GC waits, Bottlenecks

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BEFORE EXAFUSION AFTER EXAFUSION

The expected result is that GC waits have reduced latency due to elimination of the

normal kernel networking overhead.

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