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Category Archives: Oracle

Franck Pachot

#UKOUG_TECH17

By | Oracle | No Comments

Award I’ve received an award for an article I’ve written last year, the Most Read Oracle Scene Article in 2016 – Technology. I like to write for Oracle Scene magazine. It is rare today to have a magazine both available in a paper version, and also publicly available on the web. And I must say that as an author, all the people behind are doing a great work. Thanks to them and thanks for the…

 
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Michael Hein

Naming of archivelog files with non existing top level archivelog directory

By | Database Administration & Monitoring, Database management, Oracle | No Comments

In Oracle 12.2 an archive log directory is accepted, if top level directory does not exist: oracle@localhost:/u01/app/oracle/product/12.2.0/dbhome_1/dbs/ [DMK] ls -l /u02/oradata/DMK/ total 2267920 drwxr-xr-x. 2 oracle dba        96 Dec  6 05:36 arch … Now database accepts this non existing archivelog destination: SQL> alter system set log_archive_dest_3=’LOCATION=/u02/oradata/DMK/arch/arch2′; System altered. But not this: SQL> alter system set log_archive_dest_4=’LOCATION=/u02/oradata/DMK/arch/arch2/arch4′; alter system set log_archive_dest_4=’LOCATION=/u02/oradata/DMK/arch/arch2/arch4′ * ERROR at line 1: ORA-02097: parameter cannot be modified because specified value is invalid…

 
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Nicolas Jardot

DOAG 2017: Automation in progress

By | Database Administration & Monitoring, Oracle | 5 Comments

A week ago, I had the chance to be speaker at the DOAG Konferenz 2017 in Nürnberg. It’s sometimes hard to find time to be at the conferences because the end of year is quite busy at customers. But it’s also important because it’s time for sharing. I can share what I’m working on about automation and patching and I can also see how other people are doing. And it was great for me this…

 
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Clemens Bleile

DOAG 2017: avg_row_len with virtual columns

By | Database Administration & Monitoring, Database management, Oracle | No Comments

At the DOAG I attended a session “Top-level DB design for Big Data in ATLAS Experiment at CERN” provided by Gancho Dimitrov. The presentation was actually very interesting. As part of Gancho’s improvement activities to reduce space in a table he stored data in a 16 Bytes raw format (instead of a string representing hex values which requires 36 Bytes) and use virtual columns to actually calculate the real hex-string. So the original value is…

 
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Franck Pachot

12c Multitenant Internals: compiling system package from PDB

By | Oracle | No Comments

When I explain the multitenant internals, I show that all metadata about system procedures and packages are stored only in CDB$ROOT and are accessed from the PDBs through metadata links. I take an example with DBMS_SYSTEM that has nothing in SOURCE$ of the PDB. But I show that we can compile it from the PDB. This is my way to prove that the session can access the system objects, internally switching the session to the…

 
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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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