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March 2019

Hash Partitions

Here’s an important thought if you’ve got any large tables which are purely hash partitioned. As a general guideline you should not need partition level stats on those tables. The principle of hash partitioned tables is that the rows are distributed uniformly and randomly based on the hash key so, with the assumption that the number of different hash keys is “large” compared to the number of partitions, any one partition should look the same as any other partition.

dbca now makes it easy to configure OMF on file systems

Up until – and including – Oracle 12.1 I always found it not-quite-so-straight-forward to create a new database using Database Creation Assistant (dbca) and configure it with Oracle Managed Files (OMF) on a file system in silent mode. I really like to use OMF in my lab databases as it saves me a lot of typing. I have also seen Oracle databases deployed in the cloud on file systems without ASM. So I was quite happy to see the syntax for dbca -silent -createDatabase was extended.

This post has been written using Oracle 18.4.0 on Linux.

DBID Is Not Definitive When Used As An Identifier

Our Audit Trail toolkit PFCLATK has some brief documentation on the page that's linked here but in summary it is a comprehensive toolkit that allows quick and easy deployment of an audit trail into a customers database. We are currently....[Read More]

Posted by Pete On 12/03/19 At 09:20 PM

sys_op_lbid

I’ve made use of the function a few times in the past, for example in this posting on the dangers of using reverse key indexes, but every time I’ve mentioned it I’ve only been interested in the “leaf blocks per key” option. There are actually four different variations of the function, relevant to different types of index and controlled by setting a flag parameter to one of 4 different values.

The call to sys_op_lbid() take 3 parameters: index (or index [sub]partition object id, a flag vlaue, and a table “rowid”, where the flag value can be one of L, R, O, or G. The variations of the call are as follows:

Hardening and Securing The Oracle Database Training in London

I posted last week that I will teach my two day class " How to Perform a Security Audit of an Oracle Database " with Oracle University in London on the 29th and 30th April 2019. We have now added....[Read More]

Posted by Pete On 11/03/19 At 11:52 AM

Oracle Magazine

Generally my blog is just snippets of tech content that take my interest as I encounter them (most commonly when looking at AskTOM). If I think they’ll be useful, I’ll just plonk them out right there and then. If you prefer your content in longer (and more structured Smile) form, then also I publish longer form articles on Oracle Magazine every couple of months. Below is a consolidated list of my articles. I’ll try to keep this list updated as I add new ones.

Old Dog, New Tricks, Part 2
Here’s a new SQL syntax for hierarchy processing.

SQL prevents database corruption and injection, except in the ridiculous movie’s hacker scenes.

SQL is the Structured Query Language used to define and manipulate data in most of the databases in the world, and the most critical ones (banks, hospitals, airlines, secret services… ). And then, it gives the impression that with SQL you can do whatever you want, bypassing all application control, as if it were a backdoor to your database, wide opened on the network.

Superman 3 “overide all security” command

Programmers always laugh when seeing ridiculous hacking scenes in movies. In 2016 there was this “use SQL to corrupt their database” line in Jason Bourne (nothing to do with JSON or /bin/sh, by the way, it’s a movie) and recently in StarTrek: discovery series the hacking 'audit' was explained as “The probe used multiple SQL injections”. I’ve put the links at the end of this post.

Effective PeopleSoft Performance Monitoring

This advice note describes how to configure PeopleSoft systems on Oracle so that performance metrics are collected that are useful performance monitoring and subsequent performance tuning.

Stop The DBA Reading Data in Subtle Ways

The Problem: Dan asked me a question about whether the DBA can be stopped from accessing views such as V$SQL or V$SQL_BIND_CAPTURE with Database Vault because these views can be used to read data from the SGA. I have covered....[Read More]

Posted by Pete On 08/03/19 At 03:41 PM

Append hint

One of the questions that came up on the CBO Panel Session at the UKOUG Tech2018 conference was about the /*+ append */ hint – specifically how to make sure it was ignored when it came from a 3rd party tool that was used to load data into the database. The presence of the hint resulted in increasing amounts of space in the table being “lost” as older data was deleted by the application which then didn’t reuse the space the inserts always went above the table’s highwater mark; and it wasn’t possible to change the application code.

The first suggestion aired was to create an SQL Patch to associate the hint /*+ ignore_optim_embedded_hints */ with the SQL in the hope that this would make Oracle ignore the append hint. This won’t work, of course, because the append hint is not an optimizer hint, it’s a “behaviour” hint.