The average amount of time spent on writing data and index pages from a buffer pool to disk. The 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.
Average asynchronous write time is shown in milliseconds. It provides a measure of the I/O being performed for the tablespaces assigned to a buffer pool. To see elapsed asynchronous write time, check Pool Async Write Time (msec) in the Buffer Pool Details tab.