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



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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