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Category Archives: Oracle

Franck Pachot

Covering indexes in Oracle, and branch size

By | Oracle | No Comments

A covering index is an index that contains all the columns required by your query, so that you don’t have to do a TABLE ACCESS BY INDEX ROWID, which is the major cost of an index range scan. You don’t need any special feature to do that in Oracle. Just add the required columns at the end of the index. In the execution plan you will see the columns used as index keys for the…

 
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Marc Wagner

Dbvisit Standby Archive Log Daemon

By | Database Administration & Monitoring, Oracle | No Comments

Dbvisit Standby version 8 comes with a nice feature, a daemon, which gives the benefit to send and apply the archive log automatically in the background. Bypassing the system scheduling, the daemon will facilitate customer RPO (Recovery Point Objective) and RTO (Recovery Time Objective) fine tuning. Monitoring to apply logs to the Standby only when needed, will also optimize use of resources. Originally available for the Linux based environments, the feature has been made available…

 
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Franck Pachot

After IoT, IoP makes its way to the database

By | Oracle | 3 Comments

At each new Oracle version, I like to check what’s new, not only from the documentation, but also from exposed internals. I look (and sometimes diff) on catalog views definitions, undocumented parameters, and even the new C functions in the libraries. At last Oak Table World, I was intrigued by this V$SQLFN_METADATA view explained by Vit Spinka when digging into the internals of how execution plans are stored. This view has entries with all SQL…

 
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Franck Pachot

Docker: efficiently building images for large software

By | Oracle | No Comments

I see increasing demand to build a Docker image for the Oracle Database. But the installation process for Oracle does not really fit the Docker way to install by layers: you need to unzip the distribution, install from it to the Oracle Home, remove the things that are not needed, strop the binaries,… Before addressing those specific issues, here are the little tests I’ve done to show how the build layers increase the size of…

 
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Franck Pachot

Docker-CE on Oracle Enterprise Linux 7

By | Oracle | No Comments

Here is how I install the latest Docker version on Oracle Linux 7. You find several blog posts about it which all install ‘docker-engine’. But things move fast in this agile world and docker package name has changed. The Community Edition is now ‘docker-ce’ and you want this one to run the latest version.  

 
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Franck Pachot

Result cache invalidation caused by DML locks

By | Oracle | No Comments

In a previous post about Result Cache, I was using ‘set autotrace on’ in my session to see when the result cache hit saves the logical reads. I got a comment, by e-mail and with full test case, mentioning that the invalidation I had when doing some DML does not occur when autotrace is set to off. I reproduced the problem, on 18c because I use my cloud services to do my tests, but it…

 
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Clemens Bleile

Connect-times to the DB suddenly become very slow using sqlcl

By | Database Administration & Monitoring, Database management, Development & Performance, Oracle | 2 Comments

I recently wrote a couple of sql-scripts which had to run on all of my customer’s DBs. The sql-scripts had to be started from a Linux-client, which does not have any Oracle client software installed. So I thought of using sqlcl (see http://www.oracle.com/technetwork/developer-tools/sqlcl/downloads/index.html), because there is no need to “install” something then. All I needed was an installed JRE on the Linux-machine. Fortunately that was available. So I downloaded the newest version of sqlcl and…

 
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Franck Pachot

18c PDB switchover

By | Oracle | No Comments

In multitenant, the recovery and availability are at CDB level. But customers asked for a switchover at PDB level so Oracle has done that in 18c, based on refreshable PDBs. For this test I have two multitenant database on an Oracle Cloud service in 18c: CDB1 and CDB2. The only special thing I did was disable the mandatory TDE encryption, because I was not able to have the switchover working. With TDE encryption, I got…

 
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Franck Pachot

Enabled, Accepted, Fixed SQL Plan Baselines

By | Oracle | No Comments

When the documentation is not always clear, I prefer to build a test case to be sure about the behavior in different context and different versions. Here is a test on SQL Plan Management to show which plan is chosen among the different states of SQL Plan Baselines: Enabled, Accepted, Fixed. Thanks to Oracle ACE program, I have some Oracle Cloud credits to quickly provision a database, so I tested that on Oracle 18c.  

 
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