By Franck Pachot . DB_FLASHBACK_RETENTION_TARGET is set to keep enough flashback logs to be able to flashback database within the specified retention window. But it’s supposed to be a target only, meaning that on space pressure some files can be deleted. But be careful, there are cases where they are not and then the database hangs until you set a…
By Franck Pachot . Multitenant architecture is about dictionary separation. The idea is that all system metadata is stored only in CDB$ROOT so that space and upgrade time are optimized. Is it entirely true? let’s count the rows in the dictionary tables. In order to verify that, I’ve build a query that will count the rows from the dictionary tables,…
By Franck Pachot . When non-CDB has been declared deprecated, I was a bit upset because multitenant with a lone PDB just looks like an overhead of 3 containers instead of one. But with experience I changed my mind. First because the multitenant architecture brings some features that are available even without the option. And second, because this overhead is…
By Franck Pachot . Il n’a jamais été aussi facile de créer une base Oracle. Et ceci grâce au Database as a Service (DBaaS). C’est l’occasion de tester le cloud: Oracle Cloud Service offre une version d’essai de un mois. Si vous êtes proches de Genève, passez nous voir lors du SITB les 26-27 avril: https://www.dbi-services.com/fr/events-fr/swiss-it-business-sitb-du-26-au-27-avril-2016/ Mais j’ai aussi fait…
By Franck Pachot . When you create a DBaaS on the Oracle Cloud Service you have only one way to access to your database: ssh with the public rsa key you provide. Then you can open some ports to access the VM. However, from the VM you can’t access your own network. You need it to move data between from…
By Franck Pachot . Matching the Feature Usage Statistics to licensed options is not always easy. And once a feature usage is recorded, it is usually stored definitively. Let’s see how the multitenant option is recorded there. exec_db_usage_sampling I have a single-tenant database with only one user pluggable database: 16:19:20 SQL> show pdbs CON_ID CON_NAME OPEN MODE RESTRICTED ———-…
By Franck Pachot . In multitenant, the spfile parameters at pluggable database level are not stored in the spfile but in the CDB$ROOT table SYS.PDB_SPFILE$ If you open the standby database in read only for reporting, which is one reason to get Active Data Guard option, you may want different optimizer settings suited for reporting. In non-CDB it’s easy: the…
By Franck Pachot . In Multitenant, there are two ways to connect to a pluggable database. This means that if you want to prevent access to a pluggable database you need to revoke two privileges. Privilege Analysis Rather than trying with different combination of privileges there is a clever way to do it in 12c with privilege analysis (remember it’s…
By Franck Pachot . I received a question about multitenant. AWR tables are often raised as an example of Object Links because automatic workload repository is stored only in CDB$ROOT. However, neither the views DBA_HIST… nor the tables WRH$_… are defined as Object Link. Let’s explain on an example: DBA_HIST_SYSSTAT I’ll talk about all those multitenant internals in DOAG 2016…
By Franck Pachot . In multitenant, there are two goals: consolidation within the same container database and isolation of pluggable databases. I see multitenant consolidation as an extension of schema consolidation. What is not possible in schema consolidation, such as public objects name collision, is now possible with pluggable databases. 10 years ago I administrated on a database with high…
By Franck Pachot . In 12.1.0.1 the common user prefix was set to C## by an underscore parameter. In 12.1.0.2 it’s a documented parameter and you can change it. But is there any reason for that? I can think of a reason. Let’s say I want to use external authentication for my common users SQL> show parameter prefix NAME…
By Franck Pachot . Yesterday I was giving my ‘Interpreting AWR Reports’ Prezi at Oracle Midlands. There is a point where I explain that I always check the ‘Captured SQL account for …% of Total DB Time (s)’ in order to know whether I’ll get all details in the report or not. There are two main reasons why the most…
