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Extended Column Group Statistics, Composite Index Statistics, Histograms and an EDB360 Enhancement to Detect the Coincidence

In this post:

  • A simple demonstration to show the behaviour of extended statistics and how it can be disabled by the presence of histograms.  None of this is new, there are many other blog posts on this topic. I provide links to some of them.
  • I have added an enhancement to the EDB360 utility to detect histograms on columns in extended statistics.


'Extended statistics were introduced in Oracle 11g to allow statistics to be gathered on groups of columns, to highlight the relationship between them, or on expressions. Oracle 11gR2 makes the process of gathering extended statistics for column groups easier'. [Tim Hall:]

Reading the Active Session History Compressed Export File in eDB360/SQLd360 as an External Table

I am a regular user of SQLDB360 (the single distribution for Carlos Sierra's eBD360, and Mauro Pagano's SQLd360 tools) for remote performance analysis.  eDB360 reports on the whole database, SQLd360 reports on a single SQL ID.  eDB360 also runs SQLd360 reports for the top SQL statements.  Both tools extract ASH data to a flat-file.  Originally, it was intended that these were loaded with the eAdam utility, but eDB360 no longer executes the eAdam scripts itself.

Importing and Working with Exported AWR/ASH data in an Oracle database in a VirtualBox VM

A lot of my performance tuning work involves analysis of ASH and AWR data.  Frequently, I do not have direct access to the databases in question.  Sometimes, I ask clients to run eDB360 on their databases and send me the results, but sometimes I also want to work directly with ASH or AWR metrics.  So, I ask for an export of their AWR repository.
Oracle distributes a pair of scripts in $ORACLE_HOME/rdbms/admin.

Removing Unnecessary Indexes: 2. Identifying Redundant Indexes

This is the second post in a series about unnecessary indexes and some of the challenges that they present.
The EDB360 utility (see described on Carlos Sierra's Tools & Tips blog) contains a report of redundant indexes within a database. The query in this post (also available on my website) is based on the one in EDB360, but here the column list is produced with the LISTAGG analytic function.