Performance Engineering Interview Questions #15

Following are the Performance Engineering Interview Questions Set #15.

Q. 71 How can you reduce the ‘Buffer Busy Waits’ identified in the AWR report?

Ans: It can be reduced by:

  • Increasing the buffer cache size
  • Optimising application code to reduce contention on hot blocks
  • Examining segment-level statistics to identify problematic objects

Q. 72 What are wait events in Oracle, and why are they important for performance analysis?

Ans: Wait events represent the time sessions wait for resources or conditions. Analyzing wait events helps identify bottlenecks and areas where the database is not efficiently utilizing resources.

Q. 73 How do you prioritize which wait events to address from an AWR report?

Ans: Focus on wait events with the highest “Total Wait Time” or “Wait Class” percentages. Addressing the top wait events typically yields the most significant performance improvements.

Q. 74 What does a high “log file sync” wait event indicate?

Ans: It suggests that sessions are waiting for commits to complete, which involves writing redo data to disk. This could be due to a slow I/O subsystem, frequent commits, or insufficient log buffer size.

Q. 75 How can you reduce “log file sync” wait times?

Ans: Improve I/O performance of the redo logs (e.g., faster disks, SSDs), batch transactions to reduce commit frequency, or increase the size of the redo log buffer if waits are due to buffer space issues.


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