Performance Tuning Methods Author: Vladimir Andreev Semantec GmbH Lector: Stoyan Ivanov Semantec Bulgaria OOD Semantec GmbH Benzstr. 32 D Herrenberg, Germany Semantec Bulgaria OOD Hubcha Str Sofia, Bulgaria Reactive Tuning at its Best

2 About us More than ten years of Oracle-related experience Application design and development Database administration Performance tuning Performance analysis

3 Developers and DBAs Developers: Control the design and implementation Work in a sandbox No danger Low data volumes Low concurrency Different platform Incomplete system architecture Work on a schedule

4 Developers and DBAs DBAs: Have no control over the design and implementation Deal with production systems Controlled changes High availability requirements Real user and data loads Have tasks with higher priority than performance Availability Maintenance End user support

5 Tuning Modes Proactive Is planned Low time pressure Any methods and tools are allowed No scope or target Reactive Cannot be planned High time pressure Methods constrained by live data and packaged application Scope limited to a single (group of) problems A target always exists

6 The Plan for Success Must be simple and straightforward Must lead to fast solutions Must cover all possible cases

7 The Plan for Success 1. Reproduce the problem 2. Define the target 3. Find the bottleneck component 4. If the bottleneck happens to be in the database, use response time analysis to find the reason

8 Things to do first Reproduce the problem Trust the users for Effects of the problem Do not trust the users for Reasons for the problem Candidate solutions Scale down, but carefully Define the target Keep baselines

9 Find the bottleneck component Tier Walk Start from the end-user perspective Try to decompose the Application Response Time into time spent at all individual tiers Concentrate on the tier where most time is spent Inside Out Server_Idle_Time = User_Think_Time + Client_Processing_Time User Think Time can be ignored: When tuning batch jobs without user interaction By limiting the observation period to exclude user interaction

10 Tier Walk

11 Inside Out Benefits Client applications are generally not instrumented The Oracle Database Server has an excellent set of statistics: Complete Standardised Fairly well documented Tools V$ Views (and StatsPack) V$Session (Logon_Time) V$Session_Event (Event, Time_Waited) V$Session_Wait (Seconds_In_Wait) V$SesStat (CPU used by this session) STATS$Idle_Event (Event) SQL_Trace Event 10046, Level 12 tkprof, version 9.0 and above

12 Response Time Analysis Basics Response Time = Service Time + Wait Time Service Time = CPU time Wait Time = Idle Time + Non-Idle Time Non-Idle Time = I/O Waits + Other Waits System-Level Aggregated statistics prevent accurate analysis in multi-session environment Maybe useful for overall performance analysis, but not for reactive tuning Session-Level Reflect a linear (non-parallel) process Allow the tuner to ignore the other processing taking place in the server

13 OK, it is the database: CPU CPU-Bound Logical reads Inefficient SQL Inefficient Application Design (Re-)Parsing SQL with literals Shared Pool Size Invalidation PL/SQL Deterministic functions Tools: DBMS_Profiler

14 OK, it is the database: Disk I/O I/O-Bound Inefficient SQL + inadequate buffer sizes Table and index scans Disk sorts Hash Joins Inefficient Application Design: heavy client (or PL/SQL) processing Hot disks

15 Network I/O Communication stepNetwork wait event The server waits for the client to send a request SQL*Net message from client The client submits a request, which is split into several pieces by SQL*Net and the first piece is sent to the server The server waits for the next piece of the request SQL*Net more data from client The server assembles the request, processes it, and sends the first chunk of the results using send() SQL*Net message to client The server sends subsequent chunks of the result using send() SQL*Net more data to client After the last chunk is sent, the server starts waiting for the next request SQL*Net message from client

16 OK, it is the database: Contention Contention Latches and locks Shared pool Library cache Cache buffer chains Hot blocks Segment headers (freelists) Rollback segment headers Leading block of an index

17 Want to know more? Semantec GmbH., Semantec Bulgaria OOD Vladimir Andreev, Stoyan Ivanov Hubcha Str Sofia, Bulgaria +359(2) (2) (2) Company: Names: Address: Telephone: Fax: Internet: