Weekend Learning: Master reference note for "CPU time" wait events

If you have ever looked at what your database is doing in either a real time fashion, or via ASH/ADDM reports, then you have obviously seen wait events referencing the CPU and that does not mean there is a problem with the CPU or even with the database, but for the times when you are not sure make sure you have favorited the document ""DB CPU" / "CPU + Wait for CPU" / "CPU time" Reference Note" in My Oracle Support note 1965757.1 so you have a one-stop shop at your fingertips!  This would also be useful too, if you wanted to utilize it to check out possible issues when upgrading your database version or adding new features!

AWR Interval discussion

A few weeks ago I shared several posts from Doug Burns about incremental global stats, and today are several posts from Doug on AWR Internal here and here.  Why am I suddenly thinking about this subject?  Well I keep an eye on our alert which monitors ASH data every hour as I've said many, many times before and this is absolutely a good discussion about what tools are useful when (especially if you read the comments of the first AWR post from Doug).

Weekend Learning: Emergency ASH flush

Today we had to wrangle a database that was having a problem, and going through the log for the instance I found this gem:

Active Session History (ASH) performed an emergency flush. This may mean that ASH is undersized. If emergency flushes are a recurring issue, you may consider increasing ASH size by setting the value of _ASH_SIZE to a sufficiently large value. Currently, ASH size is (setting) bytes. Both ASH size and the total number of emergency flushes since instance startup can be monitored by running the following query:
 select total_size,awr_flush_emergency_count from v$ash_info;

While I knew that ASH did get flushed, I did not know about an emergency flush for ASH!  Maybe that is the parameter that Tim Gorman shared during the Hotsos Symposium this year.  So not only do we know this can pop into the database log but we are given the exact table so we can build an automated alert to tell us when ASH is flushed and how many emergencies have happened.

Weekend Learning: Using ASH Analytics in EM12c

Have you used Enterprise Manager 12c yet to drill into ASH analytic data?  If you have not had the chance, I would visit the page Kellyn Pot'vin shared via Twitter tonight where she uses EM12c to identify a negative trend and then dive into the ASH data to figure out what is going on!  This was a great article where she gives us the entire "train of thought" plus screenshots for every event so we can duplicate her efforts when we have our own problems!