The average amount of time spent on asynchronous reads of data and index pages from a tablespace into a buffer pool. The reads are performed by asynchronous engine dispatchable units (EDUs). They are asynchronous in that they occur ahead of requests from agents.
Average asynchronous read time is shown in milliseconds. It provides a measure of the I/O being performed for a tablespace. To see elapsed asynchronous read time, check Pool Async Read Time (msec) in the Tablespace Details tab.