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Category Archives: Oracle

Franck Pachot

18c Read Only Oracle Home

By | Oracle | No Comments

This is the big new feature of Oracle 18c about database software installation. Something that was needed for decades for the ease of software deployment. Piet de Visser raised this to Oracle a long time ago, and we were talking about that recently when discussing this new excitement to deploy software in Docker containers. Docker containers are by definition immutable images. You need a Read Only Oracle Home, all the immutable files (configuration, logs, database)…

 
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Franck Pachot

(DESCRIPTION_LIST=(DESCRIPTION=(ADDRESS_LIST=(FAILOVER=YES)(LOAD_BALANCE=NO)

By | Oracle | No Comments

Do you have complex connection strings with DESCRIPTION_LIST, DESCRIPTION, ADDRESS_LIST, ADDRESS and a nice combination of FAILOVER and LOAD_BALANCE? You probably checked the documentation, telling you that FAILOVER=YES is the default at all levels, but LOAD_BALANCE=YES is the default only for DESCRIPTION_LIST. But when disaster recovery and availability is concerned, the documentation is not sufficient. I want to test it. And here is how I do it.  

 
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Franck Pachot

Full page logging in Postgres and Oracle

By | Oracle, Postgres | One Comment

In my opinion, the volume of logging (aka redo log, aka xlog, aka WAL) is the most important factor for OLTP performance, availability and scalability, for several reasons: This is the only structure where disk latency is a mandatory component of response time This is a big part of the total volume of backups This is sequential by nature, and very difficult to scale by parallelizing In this post, I look at the volume of…

 
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Franck Pachot

Server process name in Postgres and Oracle

By | Oracle, Postgres | No Comments

Every database analysis should start with system load analysis. If the host is in CPU starvation, then looking at other statistics can be pointless. With ‘top’ on Linux, or equivalent such as process explorer on Windows, you see the process (and threads). If the name of the process is meaningful, you already have a clue about the active sessions. Postgres goes further by showing the operation (which SQL command), the state (running or waiting), and…

 
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Franck Pachot

12cR2 PDB archive

By | Oracle | No Comments

In 12.1 we had the possibility to unplug a PDB by closing it and generating a .xml file that describes the PDB metadata required to plug the datafiles into another CDB. In 12.2 we got an additional possibility to have this .xml file zipped together with the datafiles, for an easy transport. But that was not working for ASM files. The latest Release Update, Oct 17 includes the patch that fixes this issue and is…

 
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Franck Pachot

JAN18: Database 11gR2 PSU, 12cR1 ProactiveBP, 12cR2 RU

By | Oracle | No Comments

If you want to apply the latest patches (and you should), you can go to the My Oracle Support Recommended Patch Advisor. But sometimes it is not up-todate. For example, for 12.1.0.2 only the PSU is displayed and not the Proactive Bundle Patch, which is highly recommended. And across releases, the names have changed and can be misleading: PSU for 11.2.0.4 (no Proactive Bundle Patch except for Engineered Systems). 12.1.0.2 can have SPU, PSU, or…

 
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Franck Pachot

Multitenant, PDB, ‘save state’, services and standby databases

By | Oracle | No Comments

Creating – and using – your own services has always been the recommendation. You can connect to a database without a service name, though the instance SID, but this is not what you should do. Each database registers its db_unique_name as a service, and you can use it to connect, but it is always better to create your own application service(s). In multitenant, each PDB registers its name as a service, but the recommendation is…

 
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Thomas Rein

Migrate Windows VM with more than 4 Disks from VMware to OVM

By | Database Administration & Monitoring, Oracle | No Comments

Suppose you got an OVA image created on VMware and the VM contains more than 4 Disks and you have to migrate this machine from VMware to OVM. As first step you import the OVA into the OVM in the usual way: You see the that the appliance was imported successfully, we have 5 disks: Now you create your VM from the imported appliance: So far so good, lets have a look on our newly created VM:…

 
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Franck Pachot

Result Cache: when *not* to use it

By | Oracle | One Comment

I encountered recently a case where result cache was incorrectly used, leading to high contention when the application encountered a peak of load. It was not a surprise when I’ve seen that the function was called with an ‘ID’ as argument, which may have thousands of values in this system. I mentioned to the software vendor that the result cache must be used only for frequently calling the function with same arguments, not for random…

 
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