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Roger MacNicol

So, my Query Plan says "Table Access Full" - What Happens Next?

Roger MacNicol, Oracle



For some reports the fastest way to get them done is to use an index to go straight to the rows of interest, but sometimes the only way that makes sense is to scan the entire table. I’m the Oracle engineer responsible for the table scan driver and this talk will show what happens under the covers in simple easy to understand steps. We will look at:

  1. what is a granule in PQ
  2. how exactly does the system decided whether to use buffer cache to direct read,
  3. how is physical I/O done including Multi-Block reads and Async-I/O
  4. what wait events and stats to look at
  5. what tuning options are available to the DBA, and
  6. for the truly curious how to trace what is happening. 

Speaker Biography

I have been working in core database internals for 35 years and at Oracle for 13 years. I have worked on the implementations of tables scans, Hybrid Columnar Compression, Exadata Offload, Big Data SQL, and Database In-Memory. My current role is Software Architect for Exadata and Big Data SQL Smart Scan. Before Oracle I was the architect for Sybase IQ Query Engine - the world's first commercial columnar database and was the first chairman of the TPC-H subcommittee.