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Oracle 12c Archives - Page 2 of 28 - Blog dbi services

Mouhamadou Diaw

Automatic Data Optimization Part I : Compression Tiering

By | Database Administration & Monitoring | No Comments

Nowadays data are increasing more and more. And some challenges we can face can be how to reduce storage costs and how to improve performance. With Oracle 12c, the feature Automatic Data Optimization (ADO) can help us. In this first blog we will see how we can use ADO to compress data under predefined conditions. ADO is part of Information Lifecycle Management (ILM). Note that ADO requires Advanced Compression Option. In this article we are…

 
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Oracle Team

Keep your orapw password file secure

By | Oracle | 2 Comments

By Franck Pachot . This is a small demo I did when I’ve found a database password file (orapw) lying around in /tmp with -rw-rw-rw- permissions, to show how this is a bad idea. People think that the orapw file only contains hashes to validate a password given, and forget that it can be used to connect to a remote database without password.  

 
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Oracle Team

12c Multitenant internals: PDB replay DDL for common users

By | Oracle | No Comments

By Franck Pachot . In multitenant, you can create common Users, Roles, and Profiles. You create them in CDB$ROOT, with the CONTAINER=ALL clause (which is optional because it is the only possible value when connected to CDB$ROOT) but they are visible to all containers. As the goal of multitenant is to avoid to duplicate common metadata to all containers, You may think that they are visible through those magic metadata links. But that’s actually wrong:…

 
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Oracle Team

Drop PDB including datafiles may keep files open

By | Oracle | No Comments

By Franck Pachot . I like that Oracle drops the datafiles from the operating system when we remove them from the database (with drop tablespace or drop pluggable database) because I don’t like to have orphean files remaining in the filesystem. However, to ensure that space is reclaimed, we must be sure that Oracle did not leave a process with this file opened. Linux allows to drop an open file but then drops only the…

 
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Oracle Team

12cR2 Subquery Elimination

By | Oracle | No Comments

By Franck Pachot . More and more we can see crazy queries generated by ORM frameworks or BI query generators. They are build to be easily generated rather than being optimal. Then, the optimizer has to implement more and more transformations to get an efficient execution plan. Here is one new that appeared in Oracle 12cR2: Subquery Elimination when the subquery do not filter any rows.  

 
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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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Oracle Team

12c Multitenant Internals: compiling system package from PDB

By | Oracle | No Comments

By Franck Pachot . 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…

 
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