Tanel Poder Consulting
I solve (big) computer problems.
Talks & Interviews
Training Videos
Latest Articles
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Embedding Vectors vs. Vector Embeddings
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Video: Testing the Silk Platform in 2024 Interview (12 minutes)
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Testing the Silk Platform in 2024: Achieving 20 GiB/s I/O Throughput in a Single Cloud VM
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Visualizing Vision Transformer Embedding Vectors as Heatmaps Videos
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Visualizing and Comparing Embedding Vectors as Heatmaps
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Tracking, not Tracing, Linux Thread Activity for Complete System Visibility (eBPF Summit)
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Python Supports Profiling with Perf - How Does It Work?
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Can a User Process Consume Kernel Mode CPU Without a Syscall?
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Next Big Thing: X-Ray Vision for Linux Systems with eBPF
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Syscallargs: List All Linux System Calls With Their Arguments
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RTX4090 converted into an eGPU
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Oracle Hint Scopes and Join Level Cardinality Hint
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New Commenting System
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Oracle Shared Pool Internals: Allocated Chunk Status Indicators in Heap Dumps
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Oracle Index Parallel Degree Fix After Parallel Creation or Rebuild
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Report Current Oracle Session Wait Chains from GV$SESSION without ASH
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Advanced Oracle Troubleshooting Guide, Part 13: OStackProf for Linux, Unix & MacOSX Clients
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Testing Oracle's Use of Optane Persistent Memory, Part 2 - Fast Log File Sync Waits
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Testing Oracle's Use of Optane Persistent Memory, Part 1 - Low Latency Commits
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MySQL Now Shows its Thread Names at OS Level for Better Troubleshooting
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xb.sql and xbi.sql - Explain Oracle Execution Plans Better! (Part 2)
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My New Learning Platform and What I'm Up To in 2022
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Achieving 10 GB/s Scanning Rate in a Single Cloud VM
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Testing The Silk Platform - Hands-On Technical Analysis of High-Performance I/O in the Cloud
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Virtual Conference: Troubleshooting Very Complex Oracle Performance Problems
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Do Not Use '>' in Your Command Prompt (and How to Stay Safe in Shell)
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Is Your Linux Version Hiding Interrupt CPU Usage From You?
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Video: High Performance Block I/O on Linux
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Achieving 11M IOPS & 66 GB/s IO on a Single ThreadRipper Workstation
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Oracle Wait Event Name vs. Display Name
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Measuring Java JVM thread activity in Linux with task state sampling
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Reasons why SELECT * is bad for SQL performance
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High System Load with Low CPU Utilization on Linux?
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Hacking Session: 7 Levels of Hint Invalidity in Oracle SQL
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Hacking Session: Oracle SQL Monitoring - Understanding the Execution Timeline column and CPU usage
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Virtual Conference: Systematic Oracle SQL Optimization Interview Videos
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Oracle Fatal Background Processes
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Virtual Conference Update: Systematic Oracle SQL Optimization in 2020
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Oracle Shared Pool Internals: List Chunk Position in the LRU List
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SchedLat: a Low Tech Script for Measuring Process CPU Scheduling Latency on Linux
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Announcing My Retirement (in 2030)!
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ORA-12850: Could not allocate slaves on all specified instances error and a workaround for my scripts
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Oracle Performance Troubleshooting Without OS Access, Part 1: Identifying CPU Scheduling Latency
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Video: Troubleshooting Complex Oracle Performance Problems (Jan 2020)
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Hacking Session: Troubleshooting Complex Oracle Performance Problems (January 2020)
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help.sql: Show TPT Script Purpose and Syntax
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Oracle State Objects and Reading System State Dumps Hacking Session Video
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New scripts: xb.sql and xbi.sql - Explain Oracle Execution Plans Better! (Part 1)
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Traveling, Speaking, Training, Gluent and What I'm Up To (2019)
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Dump Current Oracle SQL Execution Plan Line ID Using Oradebug
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pSnapper: Linux Process Snapper Page and Videos
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Announcing Linux Process Snapper tool and a Linux Troubleshooting Hacking Session (3rd April 9am PDT)
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What Caused This Wait Event: Using Oracle's wait_event[] tracing
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Tutorial: Troubleshooting Linux SSH Login Delay - Why does logging in always take 10 seconds?
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Practical Linux Performance & Application Troubleshooting Training Details and Table of Contents
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Scripts for Drilling Down Into Unknown Optimizer Changes
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Visualizing SQL Plan Execution Time With FlameGraphs
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Generate Oracle SQL Monitoring Reports as HTML using SQL Developer v18.3 (no Flash needed)
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Log file switch (checkpoint incomplete) wait events and LGWR waiting for checkpoint progress
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Oracle SQL Monitoring and Advanced ASH Usage Hacking Sessions!
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Oracle SQL Tuning training & Oracle Troubleshooting training and some Linux stuff too!
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Webinar: Troubleshooting a Complex Oracle Performance Issue
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My Performance & Troubleshooting scripts (TPT) for Oracle are now in GitHub and open sourced
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Video: Oracle X$TRACE, Wait Event Internals and Background Process Communication
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Secret Hacking Session: Oracle Background Process Communication, Exotic Wait Events and Some Tracing too
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Advanced Oracle Troubleshooting seminar in 2018!
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Apache Impala Internals Deep Dive with Tanel Poder + Gluent New World Training Month
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GNW01: In-Memory Processing for Databases
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My BIWA Summit Presentations
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RAM is the new disk – and how to measure its performance – Part 3 – CPU Instructions & Cycles
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My New Youtube Channel
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Troubleshooting Another Complex Performance Issue – Oracle direct path inserts and SEG$ contention
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SQL Monitoring in Oracle Database 12c
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Advanced Oracle Troubleshooting v2.5 (with 12c stuff too)
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RAM is the new disk – and how to measure its performance – Part 2 – Tools
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RAM is the new disk – and how to measure its performance – Part 1 – Introduction
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The Hybrid World is Coming
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Old ventures and new adventures
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Advanced Oracle Troubleshooting Guide – Part 12: control file reads causing enq: SQ – contention waits?
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Sqlplus is my second home, part 8: Embedding multiple sqlplus arguments into one variable
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Oracle Exadata Performance: Latest Improvements and Less Known Features
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Oracle In-Memory Column Store Internals – Part 1 – Which SIMD extensions are getting used?
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About index range scans, disk re-reads and how your new car can go 600 miles per hour!
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Combining Bloom Filter Offloading and Storage Indexes on Exadata
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What the heck are the /dev/shm/JOXSHM_EXT_x files on Linux?
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Oracle Memory Troubleshooting, Part 4: Drilling down into PGA memory usage with V$PROCESS_MEMORY_DETAIL
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Slides of my previous presentations
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Where does the Exadata storage() predicate come from?
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Oracle X$ tables – Part 1 – Where do they get their data from?
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cell flash cache read hits vs. cell writes to flash cache statistics on Exadata
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Hard Drive Predictive Failures on Linux and Exadata
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When do Oracle Parallel Execution Slaves issue buffered physical reads – Part 2?
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When do Oracle Parallel Execution Slaves issue buffered physical reads – Part 1?
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Diagnosing buffer busy waits with the ash_wait_chains.sql script (v0.2)
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SGA bigger than the amount of HugePages configured (Linux – 11.2.0.3)
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Why doesn’t ALTER SYSTEM SET EVENTS set the events or tracing immediately?
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Advanced Oracle Troubleshooting Guide – Part 11: Complex Wait Chain Signature Analysis with ash_wait_chains.sql
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Oracle Performance & Troubleshooting Online Seminars in 2013
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Scalar Subqueries in Oracle SQL WHERE clauses (and a little bit of Exadata stuff too)
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ShowMOS: How to get rid of the annoying “The Page has Expired” dialog in My Oracle Support
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Oracle 12c: Scalar Subquery Unnesting transformation
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Oracle Database 12c R1 (12.1.0.1.0) is finally released!
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Getting the Most Out of ASH online seminar
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Forcing Smart Scans on Exadata – is the _serial_direct_read parameter safe to use in production?
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Debugger Dangers – Part 2
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List Exadata Storage Cell disk summary with cellpd.sql and cellpdx.sql scripts
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List Exadata Disk Layout and Topology with the exadisktopo scripts
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V$CELL_THREAD_HISTORY – “ASH” for Exadata Storage Cells
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Understanding what a hint affects using the V$SQL_FEATURE views
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Listing Exadata storage cells and their configuration info from V$CELL_CONFIG
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Alter session force parallel query doesn’t really force anything
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asqlmon.sql: SQL Monitoring-like execution plan line level drilldown into SQL response time
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ExaSnapper 0.7 beta download and the hacking session videos
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Peeking into Linux kernel-land using /proc filesystem for quick’n’dirty troubleshooting
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Even more Snapper – v4.03 now works in SQL Developer too!
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Manual “before” and “after” snapshot support in Snapper v4
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Snapper v4.02 and the Snapper launch party video
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Drilling Deep Into Exadata Performance with ASH, SQL Monitoring and Exadata Snapper – slides and a hacking session!
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Troubleshooting high CPU usage with poor-man’s stack profiler – in a one-liner!
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Session Snapper v4 – The World’s Most Advanced Oracle Troubleshooting Script!
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Sqlplus is my second home: Part 7 – Downloading files via sqlplus :-)
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Japanese translation of some of my blog articles
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What the heck is the INTERNAL_FUNCTION in execution plan predicate section?
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A tip for lazy Oracle users – type less with ANSI DATE and TIMESTAMP SQL syntax
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Snapper v3.61 released – and more work is in progress!
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Select statement generating redo – and lost write detection
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Sqlplus is my second home: Part 6 – Colorizing sqlplus and terminal output
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Optimizer statistics-driven direct path read decision for full table scans (_direct_read_decision_statistics_driven)
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The limitations of CURSOR_SHARING = FORCE and FORCE_MATCHING_SIGNATURE for SQL plan stability
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MOATS-like sqlplus “top” utility for RAC
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Oradebug hanganalyze with a prelim connection and “ERROR: Can not perform hang analysis dump without a process state object and a session state object.”
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Advanced Oracle Troubleshooting Guide – Part 10: Index unique scan doing multiblock reads?!
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Where is LOB data stored?
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Exadata Smart Scan predicate offloading and sequence.NEXTVAL
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Create a database link with the new host:port/service syntax
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Oracle Core: Essential Internals for DBAs and Developers book by Jonathan Lewis
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Profiling trace files with preprocessor external tables in 11g and some parallel execution hacking
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Evil things are happening in Oracle
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What the heck is the SQL Execution ID – SQL_EXEC_ID?
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V8 Bundled Exec call – and Oracle Program Interface (OPI) calls
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Full scans, direct path reads and ORA-8103 error hacking session video
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Are you getting the most out of your Exadata performance? Part 1
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What is the purpose of segment level checkpoint before DROP/TRUNCATE of a table?
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Another cache buffers chains latch contention troubleshooting example using LatchProf
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Tech Reviewer, Tech Reviewer! ;-)
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IOUG Select Journal Editor’s Choice Award 2011
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Knowing what you want to achieve before thinking of how to achieve it – a query optimization example
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Running SELECT … INTO :bind_variable from SQL
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Latch contention troubleshooting case study and Flashback Database performance issues with LOBs
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MOATS: The Mother of All Tuning Scripts!
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An index of my TPT scripts
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LOBREAD SQL Trace entry in Oracle 11.2 (and tracing OPI calls with event 10051)
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Implicit datatype conversion in the parsing phase – something new I learned today!
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ORA-4031 errors, contention, cursor management issues and shared pool fragmentation – free secret seminar!
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Exadata CAN do smart scans on bitmap indexes
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Oracle Exadata Performance series – Part 1: Should I use Hugepages on Linux Database Nodes?
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Finding Oracle Homes which Oracle instances are using on Linux
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New cursor_bind_capture_destination parameter in Oracle 11.2.0.2
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Performance Stories from Exadata Migrations
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Is this valid SQL syntax? :-)
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Snapper 3.52 – With Oracle 9.2 support!
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Asynch descriptor resize wait event in Oracle
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A little new feature for shared pool geeks :-)
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COUNT STOPKEY operation (the where ROWNUM <= N predicate) doesn't process over ~4 Billion rows and returns wrong results
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Read currently running SQL statement’s bind variable values using V$SQL_MONITOR.BIND_XML in Oracle 11.2
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The most fundamental difference between hash and nested loop joins
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Oracle Closed World presentation links
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Which number takes more space in an Oracle row?
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Exadata v2 Smart Scan Performance Troubleshooting article
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Dropping and creating tables in read only tablespaces?!
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The full power of Oracle’s diagnostic events, part 2: ORADEBUG DOC and 11g improvements
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Oracle memory troubleshooting article
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Flexible Sqlplus command line history with RLWRAP
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Execution plan Quiz: Shouldn’t these row sources be the other way around ;-)
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Quiz: Explaining index creation
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cursor: pin S waits, sporadic CPU spikes and systematic troubleshooting
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KGH: NO ACCESS – Buffer cache inside streams pool too!
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Non-trivial performance problems
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Calculate SQL_ID and SQL_HASH_VALUE from SQL text
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Oracle Latch Contention Troubleshooting
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Oracle Session Snapper v3.10
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How to CANCEL a query running in another session?
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New versions of LatchProf and LatchProfX for latch contention troubleshooting and tuning
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Oracle Troubleshooting: How to read Oracle ERRORSTACK output?!
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Using Process Memory Matrix script for calculating Oracle process memory usage on Solaris
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Oracle Wait Event reference
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Oracle Peformance Visualization…
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Bind Variable Peeking – execution plan inefficiency
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Recursive sessions…
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Sometimes things are easy (Part 1): How to fix wrapped execution plan text?
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Beyond Oracle Wait Interface – Part 2
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NULL is not zero!
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Measuring what matters
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Finding the reasons for excessive logical IOs
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Explain Plan For command may show you the wrong execution plan – Part 1
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Detect chained and migrated rows in Oracle – Part 1
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What’s a good way to learn some Oracle internals every day?
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SystemTap is production supported in Redhat EL5.4
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KGL simulator, shared pool simulator and buffer cache simulator – what are these?
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KGH: NO ACCESS allocations in V$SGASTAT – buffer cache within shared pool!
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Oracle 11gR2 has been released – and with column oriented storage option
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latch: cache buffers chains latch contention – a better way for finding the hot block
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Select COUNT(*) and COUNT(column) are different things!
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Alter system kill session and ORA-00031: session marked for kill
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An interview with me
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How to detect when a cursor was closed from SQL trace output?
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Identify the SQL statement causing those WAIT #X lines in a (top-truncated) sql tracefile
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(Secret) Preview of Oracle 12g CBO leaked from Oracle labs…
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Oracle memory troubleshooting, Part 3: Automatic top subheap dumping with heapdump
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Using Perfsheet and TPT scripts for solving real life performance problems
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ORA-04031 errors and monitoring shared pool subpool memory utilization with sgastatx.sql
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Oracle Performance Visualization videos from Sydney
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Scripts for showing execution plans via plain SQL and also in Oracle 9i
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“Free” DBA_HIST AWR views in 11g…
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I have been troubleshooting since I was a kid! :)
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Tracing Oracle SQL plan execution with DTrace
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Seminar feedback and pictures from Singapore
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Read OS environment variables using DBMS_SYSTEM.GET_ENV()
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I’m an Oracle ACE Director now :)
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Oracle 11g: Reading alert log via SQL
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Another LatchProfX use case
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The real history of Oracle database revealed!
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Oracle, Timesten and PL/SQL support
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The full power of Oracle’s diagnostic events, part 1: Syntax for KSD debug event handling
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60000 bind variables?! Maybe it’s time to use a temporary table instead…
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SQL_ID is just a fancy representation of hash value
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Performance Visualization, Capacity planning and Hotsos Symposium
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When was a table last changed?
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Multipart cursor subexecution and PRECOMPUTE_SUBQUERY hint
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Identifying shared memory segment users using lsof
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Reliable latch waits and a new blog
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Oracle memory troubleshooting, Part 1: Heapdump Analyzer
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Performance Visualization made easy – PerfSheet 2.0 beta
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A little oradebug enhancement in Oracle 11g
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Advanced Oracle Troubleshooting Guide, Part 9 – Process stack profiling from sqlplus using OStackProf
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Transportable tablespaces and ROWID uniqueness
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VLDB 2008 proceedings, Oracle optimizer plan stability, adaptive cursor sharing and SecureFiles
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Oracle hidden costs revealed, Part2 – Using DTrace to find why writes in SYSTEM tablespace are slower than in others
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Flexible sampling of any V$ or X$ view with sample.sql
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Case study on some rowcache internals, cached non-existent objects and a describe bug
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Why does even a small difference in SQL text cause a hard parse?
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Script: Display valid values for multioption parameters (including hidden parameters)
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The simplest query for checking what’s happening in a database
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Library cache latches gone in Oracle 11g
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Advanced Oracle Troubleshooting Guide, Part 8: Even more detailed latch troubleshooting using LatchProfX
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Closed database and WITH subquery
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Advanced Oracle Troubleshooting Guide, Part 7: Sampling latch holder statistics using LatchProf
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Another use case for WaitProf – diagnosing “events in waitclass Other”
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Killing an Oracle process from inside Oracle
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cursor_space_for_time To Be Deprecated
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Advanced Oracle Troubleshooting Guide, Part 6: Understanding Oracle execution plans with os_explain
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Debugger dangers
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Short note on KGX Mutexes
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Generating lots of rows using connect by – safely!
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Advanced Oracle Troubleshooting Guide, Part 5: Sampling V$ stuff with WaitProf. Really fast. Using SQL!
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Performance Tools Quick Reference Guide
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Advanced Oracle Troubleshooting Guide, Part 4: Diagnosing a long parsing issue
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Snapper shortcut
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Querying the current tracefile name, using SQL – with tracefile_identifier
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Oracle Troubleshooting with Snapper – detecting who’s causing excessive redo generation
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Performance and Scalalability Improvements in Oracle 10g and 11g
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Using autonomous transactions for sleeping
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SQL*Net break/reset to client
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SQL*Net message to client vs SQL*Net more data to client
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SQL*Net message to client wait isn’t really what it’s thought to be
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Oracle hidden costs revealed, part 1 – Does a batch job run faster when executed locally?
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Excellent article on Oracle 11g PL/SQL function result cache
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Can you write a working SQL statement without using any whitespace?
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Expensive calculator…
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Why does Oracle parameter count change during session lifetime?
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Systematic application troubleshooting in Unix
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Perl version of Snapper
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Sqlplus is my second home, part 5: Reading the name of currently executing script
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Oracle Security, Part 2: Your read only accounts aren’t that read only
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Sqlplus is my second home, part 4: Getting sqlplus parameter value into a variable
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A simple interview question
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How to resolve SQL object and column names all the way to base tables and columns in Oracle?
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Advanced Oracle Troubleshooting Guide, Part 3: More adventures in process stack
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Sqlplus is my second home, part 3: Colored selections in Windows XP command prompt
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Sqlplus is my second home, part 2: Running SQL scripts from remote locations using HTTP
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Operating systems are lazy allocating memory
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Advanced Oracle Troubleshooting Guide, Part 2: No magic is needed, systematic approach will do
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Oracle Session Snapper, part 2: Getting most out of Snapper
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Oracle 11g internals part 1: Automatic Memory Management
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Oracle Session Snapper – real-time session-level performance stats for DBAs
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Sqlplus is my second home, Part 1: HTMLizing your sqlplus output
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Session-level statspack
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A gotcha with parallel index builds, parallel degree and query plans
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My version of SQL string to table tokenizer
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Advanced Oracle Troubleshooting Guide: When the wait interface is not enough [part 1]