12c: PX Auto DOP without IO Calibration
I have upgraded one of data warehouse databases from 11g to 12c this week and noticed changes in behaviour of the PX Auto DOP feature.
Oracle¶
Bug 20214168 - Wrong Results using aggregations of CASE expression with fix of bug 20003240 present
Encountered a wrong results issue caused by Bug 20214168 - Wrong Results using aggregations of CASE expression with fix of bug 20003240 present. This post discusses possible ways to get around it.
EM 12.1.0.4 Installing recommended plugins and patches
We use the DBaaS (Database as a Service) functionality of EM Cloud Control 12c. After facing with multiple issues, it was decided to update EM and install Oracle recommended plugins and patches. This post discusses the issues that I came across during the update exercise.
Reclaim unused space from MLOG$ segments after materialized view refresh
Materialized view log space is not decreased after materialized view refresh is done. This post discusses how to reclaim the space.
Edition-based redefinition: adjunct schemas
In this blog post I would like to describe one of the basic component of Edition-based redefinition (EBR): adjunct schemas.
Function-Based index changed its definition after a rebuild
One of our developers has discovered a problem when an index column's data type changed after the index was rebuilt.
Session cursor cache count statistics incorrect with parallel queries
I have recently investigated an issue with high session cursor cache count statistics in one of 11.2.0.4 databases.
I found that some of sessions have extremely high values of these statistics.
Join elimination not performed in the presence of virtual columns on parent table
Found a case when a query joining parent and child tables did not eliminate the parent table when it seemingly could.
Suspending user session on specific enqueue
Recently I faced a strange issue with EBR (Edition-Based Redefinition). In order to understand how things work internally I decided to use DTrace.
c3p0 PROBABLYNOT connection test query
Found a frequently executed SELECT query and decided to diagnose it further.