An example of tuning — nothing special, but it does illustrate several aspects of tuning work, so I thought I’d make a blog post out of it.
Yesterday I as contacted by a development team working with a 10.2.0.4 database. Their complaint was the traditional “the system is slow”. Despite very unspecific symptoms, they were very specific about the time when it all started. I didn’t have access to AWR on that database, so instead I looked at top wait events in DBA_HIST_SYSTEM_EVENT for recent snapshots, nothing interesting. The top wait event was db file sequential read (with db file scattered read as a very distant second). Since that particular group was working with just one user in the database, I looked at ASH data for this user — same thing, just a bunch of db file seqential reads. Continue reading “SQL tuning: real-life example”