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12c Archives - Blog dbi services

Morgan Patou

WebLogic – Cannot register for disconnect events on local server

By | Application integration & Middleware | No Comments

When working with WebLogic, there will probably be a moment when you will ask yourself: damn, what is wrong? Nowadays, software are so complex that it is kind of easy to introduce bugs/non-wanted behaviors in them… In this blog, I will present a small thing that just blew my mind when I faced it: I had a fully working WLS on which I executed a WLST script in order to configure the SSL Ciphers for…

 
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Clemens Bleile

Trace files segmented in multiple parts as a workaround for bug 23300142

By | Database Administration & Monitoring | No Comments

Today I visited a customer, who deleted a Data Guard configuration (i.e. a temporary Data Guard setup through the broker was deleted). The LOG_ARCHIVE_DEST_STATE_2 on the primary database was set to DEFER temporarily. That resulted in trace-files with name *tt*.trc to become huge (GBytes after a couple of days). Analysis showed that this was caused by bug 23300142 in 12.1.0.2. See My Oracle Support Note Bug 23300142 – TT background process trace file message: async…

 
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Franck Pachot

Instance Caging and multitenant: do the right setting

By | Database Administration & Monitoring | No Comments

When you want to do instance caging, you have to set manually CPU_COUNT and to set a resource manager plan. If you set only the CPU_COUNT no instance caging will occur. Except during the maintenance window where the maintenance plan is set internally. You don’t want that kind of unpredictable behavior, so the recommandation is to always set a resource plan when you set manually CPU_COUNT. Here is another reason for such an unpredictable behavior….

 
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Franck Pachot

Adaptive Plan: How much can STATISTICS COLLECTOR buffer?

By | Database Administration & Monitoring | 7 Comments

The 12c adaptive plan prepares two join methods (Hash Join and Nested Loop), actives the one that has the better cost for the estimated cardinality and computes the point of inflection in cardinality estimation where the best cost changes to the other join method. At execution time, rows are buffered by a STATISTICS COLLECTOR operation in order to see if the point of inflection is reached. If it doesn’t, the plan continues as planned. If…

 
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Franck Pachot

12c multitenant: Cursor sharing in CDB

By | Database Administration & Monitoring | 2 Comments

In multitenant, there are two goals: consolidation within the same container database and isolation of pluggable databases. I see multitenant consolidation as an extension of schema consolidation. What is not possible in schema consolidation, such as public objects name collision, is now possible with pluggable databases. 10 years ago I administrated on a database with high level of consolidation: 3000 schemas with same structure and different data. The big scalability issue there was library cache…

 
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Franck Pachot

OCM 12c preparation: Manage PDB

By | Database Administration & Monitoring, Oracle | No Comments

Let’s see the different ways to create a PDB, with different tools. Same disclaimer here as in the first post of the series: don’t expect to get those posts close to what you will have at the exam, but they cover important points that matches the exam topics. Documentation Information about the exam says: Be prepared to use the non-searchable documentation during the exam, to help you with correct syntax. Documentation about the ‘Create and…

 
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Franck Pachot

OCM 12c preparation: Create CDB in command line

By | Database Administration & Monitoring, Oracle | No Comments

This post starts a series about things I wrote while preparing the OCM 12c upgrade exam. Everything in those posts are written before taking the exam – so don’t expect any clue about the exam here. It’s based only on the exam topics, and only those points I wanted to brush up, so don’t expect it to be a comprehensive list of points to know for the exam. Let’s start by creating a CDB manually…

 
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Franck Pachot

set “_rowsets_enabled”=false

By | Database Administration & Monitoring, Oracle | No Comments

This 12c ‘wrong results’ issue is thoroughly described by Mike Dietrich (https://blogs.oracle.com/UPGRADE/entry/switch_off_rowsets_enabled_in) and I’ve nothing to add. This blog post is there to be used as a reference for the comment in the following recommendation that we give to our 12c customers: alter system set “_rowsets_enabled”=false comment=’see http://blog.dbi-services.com/_rowsets_enabled’ scope=both; Our best practice is to document any parameter that is set as a workaround so that it can be revert back when not needed anymore.  

 
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