Performance Engineering Interview Questions #12

Following are the Performance Engineering Interview Questions Set #12.

Q. 56 What role does the buffer cache play in database performance?

Ans: The buffer cache stores copies of data blocks read from the disk. A properly sized buffer cache reduces physical I/O by satisfying requests from memory, thus improving performance.

Q. 57 How can you assess buffer cache efficiency in an AWR report?

Ans: Examine the ‘Buffer Cache Hit Ratio’ in the ‘Instance Efficiency Percentages’ section. If the ratio is close to 100% then it indicates efficient use, but excessively high values with performance issues may suggest other problems.

Refer to read more about Buffer Cache Hit Ratio and Instance Efficiency Percentage.

Q. 58 What is the ‘Redo Log Buffer’ and how does its size affect performance?

Ans: The redo log buffer caches redo entries before writing to disk. If it’s too small, processes may wait for space, leading to ‘log buffer space’ waits. Proper sizing reduces such waits and improves transaction throughput.

Q. 59 Which parameter determines the number of database buffers available in the buffer cache?

Ans: The DB_BLOCK_BUFFERS initialization parameter determines the number of database buffers available in the buffer cache.

Q. 60 What does Buffer Busy Waits indicate?

Ans: The ‘Buffer Busy Waits’ indicates that a particular block is being used by more than one process at the same.