Oracle 12c

Multitenant vs. schema based consolidation

By Franck Pachot . If you want to install multiple instances of a software, for example you host the ERP for several companies or subsidiaries, you have 3 solutions: have one database and multiple schema have multiple databases have(…)

Multithreaded 12c and ‘connect / as sysdba’

By Franck Pachot . In Oracle 12c you can run Oracle processes as operating system threads, lowering the number of OS processes. But you can’t use OS authentification: you need to provide a password. Here is a way to(…)

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.

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,(…)

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(…)

Variations on 1M rows insert (4): IN MEMORY

By Franck Pachot . Oracle In-Memory option is for reporting. Oracle has chosen an hybrid approach: maintain the In-Memory Column Store in addition of the buffer cache. Dont’ forget our In-Memory event, but for the moment, let’s try(…)

Matching SQL Plan Directives and extended stats

By Franck Pachot . This year is the year of migration to 12c. Each Oracle version had its CBO feature that make it challenging. The most famous was the bind variable peeking in 9iR2. Cardinality feedback in 11g also(…)

ALTER TABLE INMEMORY

By Franck Pachot . In-Memory Column Store is amazing. It brings very good performance to full table scans. I’t easy: just ‘flip a switch’ and you accelerate all reporting queries on your table, without thinking about what to index(…)