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.
Заметки¶
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.
Bug 4991675 - Diagnostic event improve diagnosability of data dictionary invalidation issues
In a recent MOS HOT Topics email I found a note about a new parameter to track dictionary invalidation issues: Bug 4991675 - Diagnostic event improve diagnosability of data dictionary invalidation issues (Doc ID 4991675.8)
Event 10505: CBO enable dynamic sampling dump to table
Event 10505 dumps dynamic sampling statistics to user tables.
JPPD bypassed View has non-standard group by
В одной из БД Hibernate сгенерировал новый запрос, который вызвал повышенную загрузку. Я исследовал этот запрос, оптимизируется он легко, но я выявил один интересный случай, когда JPPD (join predicate pushdown) не срабатывает для group by view.
Event 10384 level 16384: force parallel queries to run as serial
Sometimes it is useful to run parallel queries in serial mode. Event 10384 level 16384 is one of the ways to do this.