Understanding And Resolving Oracle Free Buffer Wait Contention

• It's an emotional roller coaster being an Oracle buffer header •

Free buffer waits is one of the most feared of all Oracle wait events. It requires just the right workload mix and configuration to appear. When it does appear, it affects the entire application. As Oracle DBAs, our job is to regain control of the situation and restore application performance. But it is complicated, and making the wrong move can make the situation even worse!

So, how do you quickly improve performance with a clear understanding of the situation? That's the focus of this video seminar.

This seminar is designed to take you on a journey. The journey starts with Craig clearly explaining what a free buffer wait is. Then he delves into Oracle's buffer cache focusing on the least recently used (LRU) lists and the associated algorithms. Craig even role plays as an Oracle foreground process and an Oracle buffer header to make it easy to lock the details into your brain. All the details are brought together making the cause and effect clear so the presented solutions make perfect sense! Taking it further, two solutions are implemented and the results analyzed.

Join Oracle ACE Director, Craig Shallahamer, as he take you on an unforgettable journey into the Oracle buffer cache. His goal is to help you understand and resolve Oracle free buffer waits.

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What You Will Learn

  • How to solve Oracle free buffer wait (FBW) contention
  • What exactly is a free buffer wait
  • Know the purposes of the key buffer cache lists
  • How Oracle's least recently used (LRU) algorithm works
  • The relationship between the buffer cache, LRUs, buffer headers, buffers and blocks
  • Why a free buffer wait occurs
  • How free buffer waits relate to other wait events such as db file scattered reads, write complete, read by other session waits and db file async IO submit
  • Multiple ways to reduce and/or eliminate free buffer waits
  • How to pick the best solution
  • How to retrieve and analyze FBW wait times
  • The three supporting "legs" of a free buffer wait


  • What this seminar is all about
  • Key buffer cache lists, focusing on LRUs, buffers and buffer headers
  • LRU memory serialization control (latches)
  • Oracle's cache struggles. Role Play: How a foreground process find a replaceable buffer.
  • Role play: How a buffer header moves around on an LRU list. Causing and watching FBWs occur.
  • Tracking the life of a buffer header in and out of the buffer cache
  • Exploring FBW wait times
  • The three legs of a free buffer wait. How to eliminate FBWs. Solution implementation: Bigger buffer cache.
  • Solution implementation: Adding more DBWRs
  • Resources and seminar conclusion

Seminar Videos