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Category Archives: Oracle

Franck Pachot

18c new Lost Write Protection

By | Oracle | 4 Comments

There are many layers between the Oracle Database pwrite() calls and the physical sector written on disk: filesystem, logical volume, SAN or NAS, with a lot of smart software running for Virtualisation, Compression, Snapshotting, Synchronisation… Are you sure that the changes you made to your data is actually persisted on disk, completely and without any corruption? In case of bug or crash in the storage layer, it may happen that only part of the changes…

 
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Franck Pachot

18c, Cloud First and Cloud Only features: think differently

By | Database Administration & Monitoring, Oracle | One Comment

Remember the times when the Oracle Software features were the same on all platforms? Where Oracle databases could be ported to any relevant platform? Where we were able to try any feature, freely, by downloading the latest release software? Now we need to think differently. Because: The new software is released on Cloud first The major new features will never be available on-premises The Cloud here means the Oracle Cloud – not AWS, not Azure,…

 
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Franck Pachot

A free persistent Google Cloud service with Oracle XE

By | Cloud, Oracle | One Comment

In a previous post I’ve listed several free online services which run an Oracle XE so that you can test your SQL easily. You may want use Oracle XE further, with full access to the database and its host, and still from a web browser. You probably have a Google account. Then you also have a Virtual Machine on the Google Cloud (0.5 vCPU / 1.70 GB RAM boostable to 1 vCPU / 3.75 GB)…

 
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Franck Pachot

PDB upgrade from 12c to 18c

By | Oracle | No Comments

Oracle 18c is out, in the Oracle Cloud, and the first thing I do with a new version is testing how long it takes to upgrade a previous version PDB by unplug/plug. Faster upgrade should be the benefit of having a slim dictionary where the system objects are reduced to metadata links and data links. However, it looks like upgrading the PDB dictionary still takes the same time as upgrading the CDB$ROOT. The idea is…

 
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Franck Pachot

ODA Lite: What is this ‘odacli’ repository?

By | Oracle | One Comment

When ODA Lite was introduced, with ODA X6-2 S/M/L, and now with ODA x7-2 S/M, a new ‘odacli’ was there to manage it. It will probably replace the oakcli for ODA HA as well in the future. One big difference: it uses a repository to record the configuration and the operations. I don’t really like it because when something fails you are blocked. Oracle Support can modify the directory, but they ask for an access…

 
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Nicolas Penot

Migrate Oracle Database(s) and ASM diskgroups from VMWARE to Oracle VM

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

This is a step by step demonstration on how to migrate any ASM disk groups from a cluster to another. May be use, with or without virtualization and may be used with storage layer snapshot for fast environment provisioning. Step 01 – Shutdown source database(s) on VMWARE servers Shutdown all databases hosted in the targeted Disk groups for which you want consistency. Then unmount the disk groups. $ORACLE_HOME/bin/srvctl stop database -db cdb001 $ORACLE_HOME/bin/asmcmd umount FRA…

 
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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 | 4 Comments

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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