dbi services Blog
Welcome to the dbi services Blog! This IT blog focuses on database, middleware, and OS technologies such as Oracle, Microsoft SQL Server & SharePoint, EMC Documentum, MySQL, PostgreSQL, Sybase, Unix/Linux, etc. The dbi services blog represents the view of our consultants, not necessarily that of dbi services. Feel free to comment on our blog postings.
I posted a tweet with a link to a very old document - 20 years old - about 'internals of recovery'. It's a gem. All the complexity of the ACID mecanisms of Oracle are explained in a very simple way. It was written for Oracle 7.2 but it's incredible to see how much the basic things are still relevant today. Of course, there is a reason for that: the mecanisms of recovery are critical and must be stable. There is one more reason in my opinion: the Oracle RDBMS software was very well designed, then the basic structures designed 20 years ago are still able to cope with new features, and to scale with very large databases, through the versions and the years.
The cloud has been annouced, I want to try.
In RAC, blocks are copied across instances by the Global Cache Service. In single instance, we have only two status: CR for consistent read clones where undo is applied, and CUR for the current version that can be modified (then being a dirty block). I'ts a bit more complex in RAC. Here is a brief example to show the buffer status in Global Cache.
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 set an environment so that you can still 'connect / as sysdba' to a multithreaded instance.