By Franck Pachot . LISTAGG was a great feature introduced in 11g: put rows into line with a simple aggregate function. 12cR2 adds an overflow clause to it. What happens when you have so many rows that the LISTAGG result is too long? SQL> select listagg(rownum,’,’)within group(order by rownum) from xmltable(‘1 to 10000′); select listagg(rownum,’,’)within group(order by rownum) from xmltable(‘1…
By Franck Pachot . Database on ACFS is a long story. At first, the main reason for ASM was to bypass a filesystem layer that is not required by the database. ACFS was for the non-database files that had to be accessed by all cluster nodes. But then, storage vendors and other providers came with snapshots, compression and thin provisioning…
By Franck Pachot . Here are the details about an execution plan screenshot I’ve tweeted recently because the numbers looked odd. It’s not a big problem, or maybe not a problem at all. Just something surprising. I don’t like when the numbers don’t match and then I try to reproduce and get an explanation, just to be sure there is…
By Franck Pachot . SYSDBA is powerful. You should use it only when you need to. And you should audit what is done when connected SYSDBA. This is achieved by AUDIT_SYS_OPERATION. But do you have an idea how much audit log will be generated? Note that in 12c, AUDIT_SYS_OPERATION=true is the default. The documentation says: AUDIT_SYS_OPERATIONS enables or disables the…
By Franck Pachot . When Oracle Multitenant came out in 12c, with pluggable databases, it was easy to draw them as USB sticks that you can plug and unplug to/from your Container Database (CDB). I don’t like this because it gives the false idea that an unplugged database is detached from the container. Containers In the Oracle documentation, the Concept…
Dans ce blog, je vais vous expliquer comment exporter les backups RMAN sur un « share disk » appartenant à un Domaine. Assurer la sécurité des données est l’une des tâches principales de l’administrateur : La mise en œuvre d’une protection des fichiers sensibles de la base : Fichier de contrôle Fichiers de journalisation La mise en place d’une stratégie de sauvegarde/récupération : Adaptée aux contraintes…
By Franck Pachot . The previous post partly answered to the original question (why an object link to V$SESSION is refreshed only every 30 seconds): recursive queries on shared=object views. Now let’s see what is different with fixed tables. Disclaimer: this is research only. Don’t do that anywhere else than a lab. This is implicit when the title is ‘internals’.…
By Franck Pachot . I had a comment on object links internals when creating a sharing=object view on GV$SESSION. Before posting about this specific case, I realized that I’ve never explained how a query on an object link is run on the CDB$ROOT container. Data link testcase Here is how I create the DEMOT table and DEMOV view as object…
It’s with pleasure to announced dbi services have upgrade the infrastructure for Oracle DBA essentials workshop. We have migrate the release of Oracle 11g R2 to the latest version Oracle 12c features and install the last PSU (April 2016). During this course you understand different topics: Understand the Oracle database architecture Install and Manage Oracle database Administer Oracle databases with…
By Franck Pachot . We all know what is the multitenant option: a container database (CDB) with multiple user pluggable databases (PDB). This requires Enterprise Edition plus option. But you can use the same architecture without the option and even in Standard Edition: a CDB with only one user PDB. It is called “single-tenant” or “lone PDB”. How do you…
By Franck Pachot . When you don’t have Enterprise Edition + Diagnostic Pack, you cannot use AWR but you can, and should, install Statspack. Statspack is still there, but unfortunately do not evolve a lot. The most important section, the ‘Top 5 Timed Events’ shows only foreground events, or is supposed to do so. When a user process waits on…
By Franck Pachot . I encountered recently an issue with Adaptive Plan and SPM. Documentations says that it works perfectly together but I remembered a presentation from Nelson Calero at UKOUG TECH15 mentioning strange behavior. I reproduced the issue and share the test case here as you may encounter it in 12.1 leading to regressions when you capture SQL Plan…
