This is an Exadata wait event similar to 'db file parallel read' and normally occurs during multi-block reads of non-contiguous blocks. The most common operations associated with this wait event are index range scans, index unique scans and lookups by rowid. Solutions Review solutions for db file parallel read for more information.
本文转自maclean_007 51CTO博客，原文链接:http://blog.51cto.com/maclean/1277886
