Following are the Performance Engineering Interview Questions Set #14. Q. 66 What is the difference between ‘db file sequential read’ and ‘db file scattered read’ wait events? Ans: The ‘db file sequential read’ indicates single-block reads, often associated with index lookups whereas ‘db file scattered read’ involves multi-block reads, typically from full table scans or … Read more
In AWR, the ‘Instance CPU’ table comes under the ‘Report Summary’ section. Refer to the below figure: To analyse the ‘Instance CPU’ section, you must Look at the Host CPU and Instance CPU sections. The key things to look for are the values “%Idle” in the “Host CPU” section and “%Total CPU” in the “Instance … Read more
In AWR, the ‘Top 10 Foreground Events’ table comes under the ‘Report Summary’ section. Refer to the below figure: The following metrics are available in the ‘Top 10 Foreground Events’ table of an AWR report: DB CPU It shows the total wait time for DB CPU and waiting %. Referring to Figure 01, the total … Read more
What is Buffer Hit ratio OR Buffer Hit %? ‘Buffer Hit Ratio’ is measured by the percentage of times the data block is requested by the query and available in memory. It is also called the ‘Buffer-Cache Hit Ratio’. Effective use of the buffer cache can greatly reduce the I/O load on the database. If … Read more
In AWR, the ‘Instance Efficiency Percentages’ table comes under the ‘Report Summary’ section. Refer to the below figure: The following metrics are available in the ‘Instance Efficiency Percentages’ table of an AWR report: Buffer Nowait % (Buffer Nowait Ratio) This metric provides the percentage of availability of the data buffers. This ratio gives an idea … Read more
Following are the Performance Engineering Interview Questions Set #13. Q. 61 How can lock contention be identified in an AWR report? Ans: High wait events like “enq: TX- row lock contention” or “enq: TM- contention” indicate lock waits. The “Segments by Row Lock Waits” section shows which segments are involved. Q. 62 What does the … Read more