Statistics

Oracle Rolling Invalidate Window Exceeded(3)

By Franck Pachot . This extends a previous post (Rolling Invalidate Window Exceeded) where, in summary, the ideas were: When you gather statistics, you want the new executions to take into account the new statistics, which(…)

Optimizer Statistics Gathering – pending and history

By Franck Pachot . This was initially posted to CERN Database blog on Wednesday, 12 September 2018 where it seems to be lost. Here is a copy thanks to web.archive.org Demo table I create a(…)

Oracle SPD status on two learning paths

By Franck Pachot . I have written a lot about SQL Plan Directives that appeared in 12c. They were used by default and, because of some side effects at the time of 12cR1 with legacy(…)

V$MYSTAT delta values

By Franck Pachot . Here is a little script I use from time to time to look at V$MYSTAT values and displaying on one line a set of statistics with their delta value between two calls.

12c dbms_stats.gather_table_stats on GTT do not commit

By Franck Pachot . In my UKOUG OracleScene article on 12c online statistics and GTT I mentioned the following: A final note about those 12c changes in statistics gathering on GTT. In 11g the dbms_stats did(…)

Oracle 12cR2 : Optimizer Statistics Advisor

The Optimizer Statistics Advisor is a new Advisor in Oracle 12.2. The goal of this Advisor is to check the way you gather the statistics on your database, and depending on what is found, it will makes some recommendations(…)

SQL Server AlwaysOn availability groups and statistic issues on secondaries

I would like to share with you an interesting issue you may face while using SQL Server AlwaysOn availability groups and secondary read-only replicas. For those who use secondary read-only replicas as reporting servers, keep reading this blog post because(…)

Rolling Invalidate Window Exceeded

By Franck Pachot . Today I was doing a hard parse storm post-mortem analysis. One hypothesis was rolling invalidation causing invalidation, but figures didn't match. I often reproduce the hypothesis to check the numbers to be sure I interpret them(…)

How to retrieve previous table statistics using Oracle dbms_stats

Sometimes, you need to modify the statistics of a table. There are various reasons: either for the performance analysis or because the execution plan changed. Oracle offers two methods: statistics restore or statistics export. Both are in the dbms_stats package.

Saving time and increasing service availability with MySQL Enterprise Monitor 2.3

Nowadays MySQL Databases are encapsulated into many mission critical software solutions. Lots of companies host one or many MySQL databases in their data center, sometimes even without knowing it except when the MySQL service is no more available. In order(…)