Database management

An alternative to DBA_EXTENTS optimized for LMT

By Franck Pachot . This is a script I have for several years, when tablespaces became locally managed. When we want to know to which segment a block (identified by file id, block id) belongs to, the DBA_EXTENTS view(…)

Oracle memory advisors: how relevant ?

By Franck Pachot . Do you look at memory advisors? I usually don’t but I still show them during the performance tuning workshop because there is no easy way to get an idea about memory sizing. This morning, while(…)

How to disable a SQL Plan Directive permanently

By Franck Pachot . In 12c you will see a lot of SQL Plan Directives. Some are useful to get better execution plans, but some will trigger too much Adaptive Dynamic Sampling and that can become a big overhead,(…)

Convert a snapshot standby to a new database

By Franck Pachot . A snapshot standby database is a nice solution when you want a temporary copy of the primary where you can do whatever you want (test a bug fix for example) and then convert it back(…)

12c Dynamic Sampling and Standard Edition

By Franck Pachot . 12c is coming with more dynamic sampling, now called dynamic statistics and using the new Adaptive Dynamic Sampling algorithm. The goal is to have better estimations and better estimations gives better execution plans. However, this(…)

How to import SQL Plan Directives

By Franck Pachot . Today I’ve presented SQL Plan Directives at the SOUG Romandie event. I had a question about the import/export of directives by Data Pump. The idea is that a lot of testing has been done on(…)

DBA_SQL_PLAN_DIRECTIVE.LAST_USED

By Franck Pachot . If you have read Matching SQL Plan Directives and queries using it then you know how to use the ‘+metrics’ format of dbms_xplan. 21:49:54 SQL> explain plan for select distinct * from DEMO_TABLE where a=0(…)

What that in-memory term is about, and what not

Everybody is talking about in-memory databases these days. And everybody is talking about columnar store for sets of data because this can be a benefit for analytic queries. And a lot of people start mixing these terms not realizing that(…)

List all RMAN backups that are needed to recover

By Franck Pachot . This blog post is something I had in draft and Laurent Schneider blog post reminds me to publish it. With the right RMAN configuration you should not have to managed backup files yourself. The(…)

Optimized Row Columnar (ORC) format in PostgreSQL

Nowadays everybody is talking about columnar storage format. What can PostgreSQL do in this area? There is no native support for that in PostgreSQL but thanks to the fact that PostgreSQL is highly extensible there is a(…)