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Category Archives: Oracle

Franck Pachot

Unstructured vs. structured

By | Oracle | One Comment

The title of this blog post was: “Tracing DBMS_RCVMAN for reclaimable archivelogs” until I started to write the conclusion… In a previous post I mentioned that there’s a bug with archivelog deletion policy when you want to mention both the ‘BACKED UP … TIMES TO …’ and ‘APPLIED’ or ‘SHIPPED’ as conditions for archived logs to be reclaimable. I opened a SR, they didn’t even try to reproduce it (and I can guarantee you can…

 
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Franck Pachot

Dynamic Sampling vs. Extended Statistics

By | Oracle | 2 Comments

On datawarehouse databases, I frequently recommend increasing the level of dynamic sampling because: Queries have complex predicates with AND, OR, IN(), ranges and correlated values for which the optimizer cannot estimate the cardinality properly Queries are long anyway (compared to OLTP) and can afford more parse time to get an optimized execution plan However, there’s a drawback with this approach because sometimes the dynamic sampling estimation may give bad estimations, and supersedes the static statistics…

 
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Nicolas Penot

Automate OVM deployment for a production ready Oracle RAC 12.2 architecture – (part 01)

By | Database management, Hardware & Storage, Operation systems, Oracle | No Comments

After having worked with OVM on various architectures I can say that it is a good technology to easily build virtualized environments for production applications. Because it is based on XEN and has simple ways to deal with existing storage (FC, ISCSI, NFS, …) and networking solution (bond, lacp, …) it is a robust and convenient way to virtualized IT infrastructures keeping “bare-metal” performance. Besides, it is an hard partitioning technology which is compliant with…

 
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Franck Pachot

Multitenant internals: INT$ and INT$INT$ views

By | Oracle | No Comments

This month, I’ll talk – with lot of demos – about multitenant internals at DOAG conference. The multitenant dictionary architecture starts with a simple idea: system metadata and data are in CDB$ROOT and user metadata and data are in PDB. And it could have been that simple. When a session connected to a PDB needs to read some system information, the session context is switched to the CDB$ROOT container and reads from CDB$ROOT SYS tablespace…

 
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Franck Pachot

Database is more than persistence. It is shared. My thoughts about Microservice Database.

By | Oracle | 4 Comments

The development teams often see the database as a ‘persistence layer’ only. And sometimes it is mentioned that the database is always the cause of the problems, especially when implementing continuous integration and trying to be agile. Then cames the idea to have this ‘persistence layer’ in an isolated environment, such as a docker container, with the database for each developer. However, this overlooks the real cause of the problems, which is not the persistence…

 
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