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Mouhamadou Diaw

Oracle 20c Data Guard : Standardization of Client-Side Broker Files

By | Database Administration & Monitoring, Database management, Oracle | One Comment

In an Oracle 20c Data Guard environment with a broker configured we can have following files called client-side broker files -The observer configuration file : observer.ora -The observer log file -The observer runtime datafile: fsfo.dat -The fast-start failover callout scripts (new feature in Oracle 20c) Before Oracle 20c, there was no default location for these files. Starting with Oracle 20c, now we can define a default location for all these files by setting an environment…

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Franck Pachot

Oracle ACFS: “du” vs. “df” and “acfsutil info”

By | Oracle | No Comments

By Franck Pachot . This is a demo about Oracle ACFS snapshots, and how to understand the used and free space, as displayed by “df”, when there are modifications in the base parent or the snapshot children. The important concept to understand is that, when you take a snapshot, any modification to the child or parent will [[email protected] ~]$ asmcmd lsdg DATAC1 State Type Rebal Sector Logical_Sector Block AU Total_MB Free_MB Req_mir_free_MB Usable_file_MB Offline_disks Voting_files…

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Mouhamadou Diaw

Oracle Data Guard RedoRoutes : What is Priority 8 ?

By | Database Administration & Monitoring, Oracle | One Comment

When dealing with cascading or far sync in a Data Guard environment, it is important to understand how to configure the RedoRoutes property. By default, a primary database sends redo to each transport destination that is configured in the destination. We can create more complex transport topology, depending of our environment, using the RedoRoutes property. Basically the RedoRoutes property has this format (redo_routing_rule_1) [(redo_routing_rule_n)] Where each routing rule contains a redo source field and a…

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Franck Pachot

Oracle non-linguistic varchar2 columns to order by without sorting

By | Cloud, Oracle | No Comments

By Franck Pachot . Sorting data is an expensive operation and many queries declare an ORDER BY. To avoid the sort operation you can build an index as it maintains a sorted structure. This helps with Top-N queries as you don’t have to read all rows but only those from a range of index entries. However, indexes are sorted by binary values. For NUMBER or DATE datatypes, the internal storage ensures that the order is…

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Franck Pachot

No{Join,GroupBy}SQL – Analytic Views for BI

By | Cloud, Oracle | No Comments

By Franck Pachot . Advocates of NoSQL can query their structures without having to read a data model first. And without writing long table join clauses. They store and query a hierarchical structure without the need to follow relationships, and without the need to join tables on a foreign key name, in order to get a caption or description from a lookup table. The structure, like an XML or JSON document, provides metadata to understand…

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Franck Pachot

Oracle 12c – peak detection with MATCH_RECOGNIZE

By | Cloud, Database Administration & Monitoring, Oracle | 2 Comments

By Franck Pachot . This post is part of a series of small examples of recent features. I’m running this in the Oracle 20c preview in the Oracle Cloud. I’ll show a very basic example of “Row Pattern Recognition” (the MATCH_RECOGNIZE clause in a SELECT which is documented as “row pattern matching in native SQL” feature by Oracle”). You may be afraid of those names. Of course, because SQL is a declarative language there is…

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Franck Pachot

Oracle 12c – pre-built join index

By | Cloud, Database Administration & Monitoring, Oracle | No Comments

By Franck Pachot . This post is part of a series of small examples of recent features. I’m running this in the Oracle 20c preview in the Oracle Cloud. I have created a few tables in the previous post with a mini-snowflake scheme: a fact table CASES with the covid-19 cases per country and day. And a dimension hierarchy for the country with COUNTRIES and CONTINENTS tables. This title may look strange for people used…

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Franck Pachot

Oracle 18c – select from a flat file

By | Cloud, Database Administration & Monitoring, Oracle | No Comments

By Franck Pachot . This post is the first one from a series of small examples on recent Oracle features. My goal is to present them to people outside of Oracle and relational databases usage, maybe some NoSQL players. And this is why the title is “select from a flat-file” rather than “Inline External Tables”. In my opinion, the names of the features of Oracle Database are invented by the architects and developers, sometimes renamed…

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Mouhamadou Diaw

Oracle 20c : Create a Far Sync Instance Is Now Easy

By | Database Administration & Monitoring, Oracle | No Comments

A far sync instance is like a standby instance as it can receive redo from the primary database and can ship that redo to other members of the Data Guard configuration. But unlike a physical standby instance, a far sync instance does not contain any datafiles and then can not be open for access. A far sync instance just manages a controlfile. A far sync instance cannot be converted to a primary instance or any…

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Franck Pachot

20c: AWR now stores explain plan predicates

By | Oracle | No Comments

By Franck Pachot . In a previous post https://blog.dbi-services.com/awr-dont-store-explain-plan-predicates/ I explained this limitation in gathering filter and access predicates by Statspack and then AWR because of old bugs about reverse parsing of predicates. Oracle listens to its customers through support (enhancement requests), though the community (votes on database ideas), and through the product managers who participate in User Groups and ACE program. And here it is: in 20c the predicates are collected by AWS and…

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