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.
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