Uploaded May 2026 | Updated September 2026, 2 weeks ago

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In physics there are many formulas to figure out the work of different actions. In an Oracle Database system Logical IOs (LIOs) is they way you can measure work of a statement. Generally speaking, the statement that does fewer LIOs will be the better one. Doing less LIOs means doing less work.

In this talk we discussed what exactly is this thing called an LIO. Then we will talk about how to see how many a statement does and some techniques to reduce them.

Highlights include:

01:15 - What are LIOs?
03:20 - Buffers in cache
09:05 - Dirty buffers
10:30 - Why optimize for LIOs?
14:35 - Real life example
16:05 - See LIOs in the plan
18:50 - Top reasons for high LIOs
20:30 - Correlated subqueries
24:35 - Solving with CTEs
33:40 - Solving with inline views
35:40 - One CTE/ILV
39:50 - Table and index scans
43:00 - Join order
49:15 - Notes on hints
53:25 - Know your data
55:55 - Summary