Oracle 12c

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(…)

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(…)

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(…)

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,(…)

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(…)

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(…)

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”(…)

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(…)

Migrating Oracle database from windows to ODA

Nowadays I have been working on an interesting customer project where I had to migrate windows oracle standard databases to ODA. The ODAs are X7-2M Models, running version 18.5. This version is coming with Red Hat Enterprise Linx 6.10 (Santiago).

When you change the UNDO_RETENTION parameter, the LOB segment’s retention value is not modified

Below, I will try to explain, a particular case for the general error : ORA-01555 snapshot too old error.. Normally, when we have this error, we are trying to adapt the retention parameters or to tune our queries. SQL> show(…)