Dtrace LIO with new features is released

A new version of a nifty tool to dig into internals of logical IO by Alexander Anokhin and Andrey Nikolaev

Alexander Anokhin

What’s new in DTrace LIO?
Jump to introduction: Dynamic tracing of Oracle logical I/O

1. The list of supported functions performing logical I/O is extended:
Note: some function names below are my suggestions.

Consistent gets:

  • kcbgtcr – Kernel Cache Buffer Get Consistent Read. This is general entry point for consistent read.
  • kcbldrget – Kernel Cache Buffer Load Direct-Read Get. The function performing direct-path read. Interesting detail: 10.2 the function kcbldrget is called just after kcbgtcr, in 11.2 by (from) kcbgtcr.

Current gets (db block gets):

  • kcbgcur – Kernel Cache Buffer Get Current Read
  • kcbget – Kernel Cache Buffer Get Buffer. This is analogue of kcbgcur function, as I observed this function is called for index branch and leaf blocks
  • kcbnew – Kernel Cache Buffer New Buffer
  • kcblnb (kcblnb_dscn in 11.2) – Kernel Cache Buffer Load New Buffer. The function performing direct-path load. Decoding of block coordinates is not supported…

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Reading AWR reports: case study

In my previous post I described some sections that are typically useful when interpreting AWR data. However, sometimes the answer comes from an unexpected source. For example, the workload profile section of the report contains key information for understanding what the database looks like, but it seldom gives a direct answer to the problem (except for maybe excessive parsing and excessive commits). But recently I came across a case when this section was enough to identify the root cause of a non-trivial issue: Continue reading “Reading AWR reports: case study”