The Average Async I/O Times graph plots the average amount of time spent performing asynchronous reads and writes for a buffer pool. It contains separate series for reads and writes:
Reads—Shown in light blue, this series plots the average amount of time performing asynchronous reads from tablespaces into a buffer pool.
Writes—Shown in orange, this series plots the average amount of time performing asynchronous writes from a buffer pool to disk.
The times spent on asynchronous reads and writes are averaged from statistics accumulated since a database was started or statistics were reset. They are shown in milliseconds on the vertical axis. Check these values along the horizontal axis to see how average times are changing over consecutive monitoring intervals of ten minutes.
Note: View the Statistics tab to see counts for asynchronous reads, writes, and read requests.
Asynchronous reads are performed by asynchronous engine dispatchable units (EDUs). They are asynchronous in that they occur ahead of requests from agents. Asynchronous writes are performed by database manager page cleaners. They are asynchronous in that they occur independently of query processing, in anticipation of the need for space in a buffer pool.