Hotsos Symposium Speaker – Carlos Sierra

Carlos Sierra is a returning Hotsos Symposium presenter.


Carlos SierraCarlos Sierra is the author of some popular tools for Oracle SQL Tuning: SQLTXPLAIN (SQLT), SQL Health Check (SQLHC) and Trace Analyzer (TRCANLZR) among others. He has been a speaker at several conferences related to Oracle performance, including Hotsos, OOW, UKOUG, RMOUG and IOUG.

Carlos currently works for Enkitec. Prior to Enkitec, he worked for Oracle for 17 years. Carlos is a frequent SQL Tuning practitioner constantly helping peers and other professionals to diagnose SQL statements performing poorly.

Presentation Titles

Session 1: SQL Tuning Made Easier with SQLTXPLAIN (SQLT)


Session 2: Understanding How Adaptive Cursor Sharing (ACS) Produces Multiple Optimal Plans


Session 1: SQL Tuning Made Easier with SQLTXPLAIN (SQLT): This session is an introduction to SQLTXPLAIN (SQLT) as a tool to aid in the complex task of SQL Tuning. It assumes nothing. From what is SQLT and its features, to how it is implemented and used, this presentation gives you a good idea how you can benefit of this free tool. As an additional value, since Oracle Support has been requesting the output of this tool on most Query Tuning Service Requests (SR), by learning how to use the right SQLT method, you may help to expedite the resolution of your own SR! During this session you will see how SQLT is installed and how the most common methods - XTRACT and XECUTE are used. A navigation through the main output is also part of this SQLT introductory session.

Session 2: Understanding How Adaptive Cursor Sharing (ACS) Produces Multiple Optimal Plans: This session is about how Adaptive Cursor Sharing (ACS) actually works. How does a bind sensitive cursor become bind aware? What are those "ACS buckets"? How does the "Selectivity Profile" work? Why does your SQL become bind aware, and why does it not sometimes? How is it that ACS interacts with SQL Plan Management (SPM)?

These and other questions about ACS are answered in detail during this presentation. Some live demonstrations are used to illustrate the ramp-up process on ACS and how some child cursors are created then flagged as non-shareable.

You will also "see" how the ACS Selectivity Profile is adapted as new executions make use of predicates with new Selectivities. ACS promotes Plan Flexibility while SPM promotes Plan Stability. Understanding how these two interact becomes of great value when some intervention is needed to restore this delicate balance.

Presentation Materials

Presentation materials are available online to attendees only.


The speaker schedule is as follows: