Monitoring I/O by Function

The I/O Function charts determine I/O usage level by application or job. The component-level statistics give a detailed view of the I/O bandwidth usage, which you can then use in scheduling jobs and I/O provisioning. The component-level statistics fall in the following categories:

• Background type

  This category includes ARCH, LGWR, and DBWR.

• Activity

  This category includes XDB, Advanced Queuing (AQ), Data Pump, Recovery, and RMAN.

• I/O type

  The category includes the following:

  • Direct Writes

    This write is made by a foreground process and is not from the buffer cache.

  • Direct Reads

    This read is physical I/O from a data file that bypasses the buffer cache and reads the data block directly into process-private memory.

  • Buffer Cache Reads

• Others

  This category includes I/Os such as control file I/Os.

To monitor I/O by function:

1. Access the Performance page, as explained in “Monitoring User Activity”.

2. In the instance activity chart, click I/O.

   The Latency for Synchronous Single Block Reads, I/O Megabytes per Second, and I/O Requests per Second charts appear.

3. For I/O Breakdown, select I/O Function.

   The I/O Megabytes per Second by I/O Function and I/O Requests per Second by I/O Function charts appear.

   The example in Figure 4-4 shows that a significant amount of I/O is being performed by the log writer. The log writer activity peaked at approximately 600 I/O requests per second.

4. Click the largest colored area on the chart or the corresponding function in the legend to drill down to the function with the highest I/O rate.

   An I/O Throughput by I/O Function page appears with details about the selected category.

   You can view real-time or historical data for details on I/O megabytes or I/O requests.

See Also:

• Oracle Database Concepts to learn about database background processes such as ARCH, LGWR, and DBWR