As customer with Foglight 5.6.3 received the following alarm:
Foglight Cartridge for Oracle has generated a Critical alarm for Oracle cluster node MYSERVER-INSTANCE on host server.example.com.
Alarm: DBO - Parallel Serialized (alarm group: Performance)
Message: The number of requested parallel queries that serialized due to lack of resources is 118.00.
Created on: Tue Sep 11 02:03:39 CDT 2012
When the customer goes to the real time of the alarm, it only offers him current time when inquiring by session in Foglight (presumably because only 60min of session info is available).
When we look at the SQL Statement information in Performance Analysis, the Degree of Parallelism for all the historical sessions is 1.
Is there a way to see what historical sessions are affected when the parallel queries are serialized?
In the Foglight Cartridge, there wouldn’t be a way of seeing historical sessions, the database drilldowns only have information for the last hour.
In regards to the parallelism question, this is valid because the statement It could have occurred in SQL that is not in the top 20 SQL Statements. This means that they will appear in the instance overview but not appear in the Top SQLs.
In Performance Analysis, the Sessions info is available for the last one hour only under Real Time tab. After one hour, the data is visible in History tab, under different dimensions tabs (such as per DBuser, OSUser, Program etc.). The degree of parallelism can be seen for all captured SQL statements – both at Real Time and History level.