Oracle

ROWNUM vs ROW_NUMBER() and 12c fetch first

By Franck Pachot . Prior to Oracle 12c, there were two ways to do ‘top-n’ queries: use rownum after sorting rows with “order by” use row_number() over (order by) Top-n queries are usually required for result pagination. The application(…)

Oracle 12c CDB – metadata & object links internals

By Franck Pachot . Warning: this is only geek stuff about internals on multitenant database dictionary, metadata, and object links. It has nothing to do with the operations that you can do on your database. Don’t try that in(…)

Oracle 12c Adaptive Plan & inflection point

By Franck Pachot . The Oracle 12c Adaptive Plan feature was already presented by Nicolas Jardot in OOW 2013: Solving customer issues with the 12c Optimizer. I recently had to answer several questions about its behavior at execution(…)

Best practice for the sending of an Oracle execution plan

By Franck Pachot . You have a query that takes too long and you want help to analyze the execution plan? Then you need to get it with relevant information, and correctly formatted. Autotrace is not a good option(…)

The consequences of NOLOGGING in Oracle

By Franck Pachot . While answering to a question on Oracle forum about NOLOGGING consequences, I provided a test case that deserves a bit more explanation. Nologging operations are good to generate minimal redo on bulk operations (direct-path(…)

Investigating Oracle lock issues with event 10704

By Franck Pachot . Did you ever encounter unexplained Oracle lock issues? They may be coming from unindexed foreign keys (which is worse in 11g). It’s not easy to monitor. Of course you can check Oracle locks from V$LOCKED_OBJECT, but(…)

Oracle 12c In-Memory option: waiting for 12.1.0.2

By Franck Pachot . Oracle has announced a big feature that should come in the next 12c patch set: the In-Memory option. It will soon be in beta version, so nothing will be published about it until it(…)

Oracle Partitioned Sequences – a future new feature in 12c?

By Franck Pachot . Disclaimer: I'll talk about an undocumented feature that appeared in Oracle 12c - undocumented except if you consider that being exposed in DBA_SEQUENCES as the PARTITION_COUNT is a kind of documentation. So, as the syntax is(…)

Oracle et Dbvisit Replicate pour migrer sans arrêt de service… et sans stress

By Franck Pachot . Je viens d’assister au Webinar Zero Downtime Migration pour Oracle, présenté par Chris Lawless qui est récemment passé de Product Manager Golden Gate à Product Manager Dbvisit.  Je vais détailler ici un point très(…)

Oracle is hanging? Don’t forget hanganalyze and systemstate!

By Franck Pachot . sqlplus / as sysdba oradebug setmypid oradebug unlimit oradebug hanganalyze 3 oradebug dump ashdumpseconds 30 oradebug dump systemstate 266 oradebug tracefile_name Your Oracle database – production DB, of course – is hanging. All users are blocked.