control file sequential read等待事件

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.