Oracle

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(…)

Show the Top 10 events from latest AWR snapshot

By Franck Pachot . Want to display a specific section from the latest AWR report? I'll share the script I use to get something like that:(…)

Parallel DML in 12c

By Franck Pachot . Following a question from Randolf Geist (who can imagine that there is something about parallel query that Randolf didn’t know?), I get back to some notes I’ve taken when 12c was out and I’ve(…)

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.

Flame Graph for quick identification of Oracle bug

By Franck Pachot . Most of my performance stores start with a screenshot of Orachrome Lighty my preferred tool to have a graphical view of the database performance, in Standard and Enterprise Edition without any options:(…)

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(…)