Oracle IO Latency Test
Functions such as direct reads, direct writes, buffer cache reads, DBWR etc., often generate a high level of I/O activity on the storage sub-system of Oracle. If the Oracle storage is not sized right to handle the I/O load, then one/more of these mission-critical functions may significantly slowdown (i.e., take more than 500 milliseconds to complete), thus delaying critical database operations. In the event of such a slowdown therefore, administrators must be able to quickly and accurately pinpoint the latent function and determine what is ailing that function, so that the configuration of the Oracle server or its storage sub-system can be fine-tuned to avoid such anomalies. This is where the Oracle IO Latency test helps. This test automatically identifies those functions that are taking more than 500 milliseconds to complete. For each of these functions, this test reports the size of the I/O generated by that function and exactly how much time Oracle’s storage sub-system takes to process this I/O load. In the process, the test turns the spotlight on the latent functions and reveals if the high I/O latency is due to a poorly configured storage system.
Target of the test : An Oracle 12c server
Agent deploying the test : An internal agent
Outputs of the test : One set of results for every I/O function that is taking more than 500 milliseconds to complete.
|
Measurement | Description | Measurement Unit | Interpretation |
---|---|---|---|
IO size: |
Indicates the current size of the I/O generated by this function. |
Bytes |
This is a good indicator of the current I/O workload on the Oracle storage. |
IO latency: |
Indicate the total I/O latency of this function. |
Msecs |
Compare the value of this measure across functions to know which function is the most latent. |
Average IO latency: |
Indicates the average I/O latency of this function. |
Msecs |
This represents the time taken by the storage sub-system to process a single byte of I/O requests for the function. A very high value is indicative of the inability of the storage system to process requests for a function quickly. This could be because the storage system is not configured with adequate space. You may want to consider resizing the storage system to ensure better I/O throughput. |
Max IO latency: |
Indicates the maximum I/O latency for a single byte of requests for this function. |
Msecs |
A high value is a cause for concern, as it indicates a potentially latent function. |