David Fitzjarrell

Oracle 12c (version 12.1.0.2) offers the option of using in-memory processing to speed things along. Called the In-memory option, it’s installed when you install the 12.1.0.2 software. Using it can make a considerable difference in processing speed, provided you have sufficient resources (RAM) available. Let’s revisit an older example, on Bloom filters, and see if […]

An interesting issue presented itself just recently with a logical standby database I manage. The database is used for generating reports and the client wanted to skip all DML activity for a given schema as it wasn’t necessary for reporting purposes. I had done this in version 10.2.0.x; it was a simple procedure: alter database […]

In a forum I frequent the following question was raised: “We see some sqls that have been running for a long time in our prod DB, 11.2. when we check the v$session, i see null sql ids for them. The sql_address shows up as 00. I would like to know what these sqls are doing […]

In Oracle releases 10.2.0.x and later join processing can be made more efficient by the use of Bloom filters, primarily to reduce traffic between parallel query slaves. What is a Bloom filter? Named after Burton Howard Bloom, who came up with the concept in the 1970s, it’s an efficient data structure used to quickly determine […]

An oft-used (and subsequently oft-abused) execution path is parallel execution, usually ‘instigated’ by some sort of parallel hint. Developers, albeit with the best intentions, misuse and abuse this mechanism because of faulty logic, that ‘logic’ being that if one process executes in X amount of time then Y parallel processes will execute in X/Y amount […]

A long while back someone asked the following question, which seems simple enough: Is there a quick way to convert week number (of the year) to start date of that week? EX: If I pass week number as 1 then it should return 1/1/2009 If I pass week number as 7 then it should return […]

Recently I’ve noticed the occasional thread in Oracle newsgroups and lists asking about hugepages support in Linux, including ‘best practices’ for hugepages configuration. This information is out on the ‘world-widreme web’ in various places; I’d rather put a lot of that information in this article to provide an easier way to get to it. I’ll […]

Exadata is a powerful system, able to provide exceptional performance. Much of this peformance is due to Smart Scans, Exadata’s mechanism for shifting the workload to the storage cells and having them filter and reduce the amount of data the database servers must process. Not every Smart Scan that starts ends up completing, though. Oracle […]

Performance is one of the big watchwords in the IT industry; nowhere is it more often used than in the database arena, and it’s usually not a good sign. End users know nothing, really, of the inner workings of the database yet they are the first to point the ‘finger of blame’ at the database […]

Chained and migrated rows in an Oracle database can seriously impact I/O performance, especially with Exadata. In a ‘normal’ Oracle database [read that as “non-Exadata, non-ASM” database] chained rows, in small numbers where that usually means 1% or less of the total rows in a table, are generally a nuisance. The performance hit they generate […]

A recent IT-related survey had in its list of questions one rather interesting offering: “Are there any safeguards preventing the DBA from accidentally dropping a table?” That is probably not a commonly considered aspeect of data security however it is an issue that should be voiced and addressed. How do you ensure that the DBA […]

It is entirely possible with later releases of Oracle to use a non-unique index to enforce a primary key constraint. An advantage of this strategy is the index remains if the constraint is, at some time dropped, provided the index was not created as part of the ‘add constraint’ statement. Disadvantages to this strategy can […]