Performance

DataBase Cloud Service performance – CPU

By Franck Pachot . In the previous blog post I've measured the physical i/o performance, with SLOB. We can run the same with a small size of data and a large buffer cache(…)

DataBase Cloud Service performance – IOPS

By Franck Pachot . Having a database in the cloud is very nice. You add storage with a few clicks. You don’t have to think about the storage type (DAS, SAN, NAS), size of disks, stripe size, SSD, etc.

Don’t use the default database file autogrow settings !

I often noticed default values for database file autogrow settings during my audits. You don’t trust me? Let me talk about a funny story about an incredible (and extreme) situation that concerns a transaction log file and its default settings.

Does the block size matter?

By Franck Pachot . The default block size is 8k in Oracle. This is the most common. Sometimes, people create the database with 16k block size for datawarehouses. You can also find some 32k block size, but less common(…)

Can you have pending system statistics?

By Franck Pachot . Your system statistics seems to be wrong and you want to gather or set more relevant ones. But you don’t want to see all your application execution plans changing between nested loops and hash joins.

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,(…)

SQL Server 2016 CTP2 : first thoughts about tempdb database

In my first blog about SQL Server 2016, I noticed during the SQL Server installation process that we are able to configure the number of files for tempdb. This is surely a great improvement(…)

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(…)

Variations on 1M insert (6): CPU Flame Graph

By Franck Pachot . If you followed the 1M rows insert variations, you have seen how something simple brought me into an investigation with the latest tools available to see where the time is spent. When the time is(…)