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Oracle 12c

Statspack with Oracle Database 19c and Multitenant

Introduction When it comes to performance analysis on Oracle databases, everybody think about Diagnostic Pack. This is a very complete tool and it brings much more metrics than a DBA can analyze. But there is a big drawback with this tool: it’s not included in Standard Edition and it’s an option with Enterprise Edition. If you don’t have this tool,… 

5 things that aren’t true about RMAN

Introduction RMAN backups are not a hot topic today. This is because it didn’t evolve that much in 12c/18c/19c, and most of the databases are now protected by a good backup strategy since years, and no changes are needed. Furthermore, Disaster Recovery solutions are more and more deployed, and all the flashback technologies embeded in the database are well known.… 

Upgrade to Oracle 19c – performance issue

In this blog I want to introduce you to a workaround for a performance issue which randomly appeared during the upgrades of several Oracle 12c databases to 19c I performed for a financial services provider. During the upgrades we ran into a severe performance issue after the upgrades of more than 40 databases had worked just fine. While most of… 

Duplicate Database on ODA X4

By Mouhamadou Diaw The ODA X4 is still in use for some customers. The last time I was asked to validate the backups . Let me explain the context. Actually the backups are done via RMAN on local in a NFS share. After these backups are backep up by Netback on tape. The goal was just to validate that the… 

Oracle non-linguistic varchar2 columns to order by without sorting

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… 

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

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… 

Oracle 12c – global partial index

By Franck Pachot . We have an incredible number of possibilities with Oracle. Yes, an index can be global (indexing many partitions without having to be partitioned itself on the same key) and partial (skipping some of the table partitions where we don’t need indexing). In the previous post of this series of small examples on recent features I partitioned… 

Oracle 12c – reorg and split table with clustering

By Franck Pachot . In this series of small examples on recent features, I have imported in a previous post, the statistics of covid-19 per day and per countries. This is typical of data that comes as a time-series ordered by date, because this is how it is generated day after day, but where you probably want to query from… 

Oracle 12c – peak detection with MATCH_RECOGNIZE

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… 

Oracle 12c – pre-built join index

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… 

Speed up datapump export for migrating big databases

Introduction Big Oracle databases (several TB) are still tough to migrate to another version on a new server. For most of them, you’ll probably use RMAN restore or Data Guard, but datapump is always a cleaner way to migrate. With datapump, you can easily migrate to a new filesystem (ASM for example), rethink your tablespace organization, reorganize all the segments,…