Oracle

Oracle IOT: when to use Index Organized Tables

By Franck Pachot . When can we use IOT? That’s a question I had when giving recently the Oracle DBA essentials workshop. the DBA Essential is very dense and there is only half a day about performance. We(…)

Oracle system statistics: Display AUX_STATS$ with calculated values and formulas

By Franck Pachot . System statistics can be gathered in NOWORKLOAD or WORKLOAD mode. Different values will be set depending on that and the others will be calculated – derived from them. We can see defined values from SYS.AUX_STATS$(…)

How to measure Oracle index fragmentation

By Franck Pachot . At Oracle Open World 2014, or rather the Oaktable World, Chris Antognini has presented ‘Indexes: Structure, Splits and Free Space Management Internals’. It’s not something new, but it’s still something that is not(…)

How to measure Exadata SmartScan efficiency

By Franck Pachot . 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(…)

Thinking about downgrading from Oracle Enterprise to Standard Edition?

By Franck Pachot . 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(…)

Oracle: How to move OMF datafiles in 11g and 12c

By Franck Pachot . 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(…)

Resize your Oracle datafiles down to the minimum without ORA-03297

By Franck Pachot . 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(…)

What’s the consequence of NOLOGGING loads?

By Franck Pachot . 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(…)

Oracle 12.1.0.2.1 Set to Join Conversion

By Franck Pachot . 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(…)

Oracle 12.1.0.2: Wait event histograms in μs

By Franck Pachot . When an Oracle Database spends a high percentage of its DB time in User I/O, I usually check the wait event histograms in order to see if the storage system is working well. But today,(…)