This is a read from a single copy of the control file. This happens in many cases. For example, while: Making a backup of the controlfiles Sharing information (between instances) from the controlfile Reading other blocks from the controlfiles Reading the header block Solutions Problem: If wait time is significant, it usually means there's an I/O problem. Find out whether the waits are on particular copy of the controlfile and, if so, whether its I/O path is saturated. The following query can be used to find which controlfile is being accessed. It has to be run when the problem is occurring: select P1 from V$SESSION_WAIT where EVENT like 'control file%' and STATE='WAITING'; Possible solutions: Move the problematic controlfile copy to a less utilized disk. Use Asynchronous I/O if available.
本文转自maclean_007 51CTO博客，原文链接:http://blog.51cto.com/maclean/1277900
