Several reasons.
But here's one very specific example which came from an error during the parse
process which wasn't fatal to the call but caused significant performance
issue. Probably not relevant to your case.
This was due to Dump Online Redo for Buffers in Pin History
https://orastory.wordpress.com/2012/05/09/why-did-that-report-run-slow-ash-says-log-file-sequential-read/
Date: Thu, 21 Apr 2016 15:04:51 +1000
Subject: log file sequential reads
From: jack@xxxxxxxxxxxx
To: oracle-l@xxxxxxxxxxxxx
Hi All
I am running a merge statement (11.2.0.3 on AIX with dataguard) and this "log
file sequential read" shows up as one of the top waits.I did a bit of searching
and other than logminer (which we do not use) I dont see much info out
there.Any hints where I can start looking next.
On a near identical Dev environment we do not have these waits.
Jack van Zanen
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