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Hi Olivier,DELAYED_DURABILITY doesn't change the SQL Server behavior of opening the data and log fil...
Hi David,Thanks for this demo with write functions. As much I know, SQL Server always access files (...
Olivier Berthommé
Thank you for your feedback. I will build a test environment and realize a guide to deploy Grid Infr...

Hi Greg,

Thanks

great job Dave ! thanks

greg
Blog dbi bloggers Franck Pachot

Franck's blog

Blog of Franck Pachot, Consultant at dbi services

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Franck Pachot

Franck Pachot

Franck Pachot is Consultant at dbi services. He has 20 years of experience in Oracle databases. Through his expertise as a DBA, Oracle expert, data architect, and performance specialist, he is able to cover all database areas: architecture, data modeling, database design, tuning, operation, and training. Franck Pachot knows how to enable an efficient collaboration between the developers and the operational team when it comes to troubleshooting issues or performance tuning. He has passed the OCP certifications from 8i to 12c, is also Certified Expert for Oracle Database 11g Performance Tuning, and now achived the highest level of certification: Oracle Master Certified OCM 11g. Prior to joining dbi services, Franck Pachot was Oracle Consultant at Trivadis in Lausanne. Previously, he worked in several countries and environements, always as a consultant. Franck Pachot holds a Master of Business Informatics from the University of Paris-Sud. His branch-related experience covers Financial Services / Banking, Public Sector, Food, Transport and Logistics, Pharma, etc.


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I'm currently following the session 'Real-World Performance of Star and Snowflake Schemas' with Michael Hallas, Andrew Holdsworth, John Clarke. It's really a good presentation. the Real Performance team tries to spread messages about how to design for performance. But today I'll not blog about what I've seen but about what I've not seen. Everybody talks about those nice 12c features that are useful in BI workloads, such as adaptive joins, adaptive parallel distribution, vector 'in-memory' aggregation, etc. Nobody talks about Adaptive Bitmap Pruning.

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Usually, the logical replication of changes uses the primary key. Each row updated or deleted generate a statement to be applied on the target, which affects only one row because it accesses with the primary key. If there is no primary key, we need to have something unique and at worst it is the whole row. But sometimes old applications were designed before being implemented into relational database and have no unicity. It it a problem for logical replication? We will see that Dbvisit replicate can address that.
 
Here is the case I encountered at a customer. The application has a master-detail table design, and the detail tables are inserted/deleted all together for the same master key. And there is no primary key, and even nothing unique. The only value that may help is a timestamp but sometimes timestamps do not have the sufficient precision to be unique. And anyway, imagine what happens if we change back the system time, or during daylight saving changes.
 
At dbi services we have very good contact with our partner Dbvisit and it's the kind of question that can be addressed quickly by the support. Anyway, I was at the Oracle Open World and then was able to discuss directly with the Dbvisit replicate developers. There is a solution and it is even documented.

The basic issue is that when the delete occurs, a redo entry is generated for each row that is deleted and then Dbvisit replicate generates an update statement to do the same on the target. But when there are duplicates the first statement will affect several rows and the next statement will affect no rows.

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Do you know Delphix? The first time I heard of it was from Jonathan Lewis. And from Kyle Hailey of course. So it's not only about agile and virtualization. It's a real DBA stuff. So as I did yesterday with Dbvisit #repattack let's install the demo.

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Oracle Open World is not only conferences but also practice and networking. Today at the OTN lounge have installed the following demos on my laptop:

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A thread on OTN Forum about Exadata came to the following question: "But how can I monitor if it is effectively used or not?". This is a common question. There are 3 exclusive features coming with Exadata, and instance statistics can show their usage. Even better: two of them can even be checked on your current (non-Exadata) system. And that is good to foresee how Exadata can improve your workload.

Tagged in: Exadata Oracle
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You are using an Oracle Enterprise Edition and thinking about downgrading to the Standard Edition? In this case, you must be sure that your applications are compatible. It's not something easy to check. Here are a few ideas.

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With OMF datafiles, you don't manage the datafile names. But how do you set the destination when you want to move them to another mount point? Let's see how easy (and online) it works in 12c. And how to do it with minimal downtime in 11g.

Tagged in: Oracle
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Your datafiles have grown in the past but now you want to reclaim as much space as possible, because you are short on filesystem space, or you want to move some files without moving empty blocks, or your backup size is too large. ALTER DATABASE DATAFILE ... RESIZE can reclaim the space at the end of the datafile, down to the latest allocated extent.

Tagged in: Oracle resize
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When you load data in direct-path and have the NOLOGGING attribute set, you minimize redo generation, but you take the risk, in case of media recovery, to loose the data in the blocks that you've loaded. So you probably run a backup as soon as the load is done. But what happens if you have a crash, with media failure, before the backup is finish?
I encountered recently the situation but - probably because of a bug - the result was not exactly what I expected. Of course, before saying that it's a bug I need to clear any doubt about what I think is the normal situation. So I've reproduced the normal situation and I'm sharing it here in case someone wants to see how to handle it.

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Recently, I described the Partial Join Evaluation transformation that appeared last year in Oracle 12c. I did it as an introduction for another transformation that appeared long time ago in 10.1.0.3 but was not used by default. And even in the latest Oracle 12c patchset 1 (aka 12.1.0.2.0) it is still not enabled. But it's there and you can use it if you set optimizer_features_enabled to 12.1.0.2.1 (that's not a typo!).

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