There are a number of techniques you can use to speed up an Oracle Import, some of which I'll describe here. This is not any attempt at a comprehensive list, just some of the main techniques I have used that can really speed up some parts of an import. I've seen a standard import come down from 2.5 hours to about 0.75 hours using these techniques.
The first thing to realise is that (more...)
To try and keep a longer story as short as possible I needed to package up the Python run time environment to ship along with a Python based application I had written. And in this case the target platform was Windows, though the solution will also work for Linux or any other platform (however most Linux distributions will already have Python on them). I needed to ship Python itself with my application to guarantee that (more...)
Some time ago I dealt with a system that was experiencing high "log file sync" times, as well as other RAC related waits ("gc buffer busy" and "gc cr block busy"). Initially I assumed that the "log file sync" waits and the RAC Global Cache waits were independent of each other, but it turned out that they were interlinked. This post is mainly to make other people aware that on a RAC system there is (more...)
I needed to "play" with Oracle VM and learn how to use it for some upcoming work involving virtual machines. Oracle VM (not VirtualBox) is virtualization software that installs directly onto a system i.e. it installs onto "bare metal" and does not need a host operating system. The problem I had was that I had no "spare" unused system on which I could install Oracle VM. I really wanted to be able to install (more...)
I've previously covered a number of queries that can be combined together to pull out key statistics from the Oracle AWR data for each snapshot it makes, which you could use to analyse the performance of a system. One example would be to use this to look at how the (more...)
This is the last of the main set of posts on this topic. As for the last post, I'll try and keep this brief and post the SQL involved.
Another data set we can look at is on SQL statements i.e. statistics collected by AWR on individual SQL statements, (more...)
So far our AWR report query shows overall duration between two consecutive snapshots, database time (i.e. doing work), SQL execution time (may be lower), total wait time, wait time by class, and some common specific wait events. We know how busy the database was and how much time it (more...)
Given the previous sub-query for total wait times including class level waits from the AWR snapshot data, we are going to extend that particular sub-query in order to add some extra wait event data items to it. This will give us a further breakdown of what the major wait events (more...)
So far I've shown the skeleton of a query that lists out some key activity data values from all the data captured by AWR in its regular snapshots. So far we've only extracted a few time based data values:
- Duration - real clock time that occurred between the AWR 2 (more...)
Following on from my previous post on doing summary reports on the data captured in the AWR. Here is some example output from using that query, and a useful statistic you can derive from the output data it produces.
The previous query just gave us 3 time values:
The addition of the Automatic Workload Repository (AWR) in Oracle 10g was a good thing, as its regular hourly snapshots collect and store a number of database wide activity statistics which allows historical reporting later on. However, the Oracle supplied standard AWR report (
) only provides detailed information (more...)
On the one hand source code control can be a nightmare involving complicated tools and formal processes, but on the other hand the ability to track the history of changes to a file can be really useful. With complicated SQL queries and stored procedures, seeing what changed between each major (more...)
I find that during my technical work on Oracle and Performance Tuning there are a few key pieces of software that I keep coming back to again and again. They are not directly related to databases, and are really more like technical tools that help me do my work better. (more...)
The Oracle Database software is only "supported" on Red Hat Enterprise Linux and Oracle Enterprise Linux I believe. But it can be made to work on many other Linux distributions one way or another, as a lot of the stuff is the same or equally available on other Linux distributions. (more...)
I really like the Python
programming language for general purpose programming and quickly putting together little utilities. There are similarities to Perl in terms of being an interpreted language with powerful data processing capabilities, but there the direct comparisons end. Python is a more modern language than Perl, and has (more...)
I was trying to set up Data Guard between two servers and I kept getting connection errors from RMAN on the primary to the secondary:
RMAN> connect auxiliary sys/syspassword@dgtest_stdby
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-04006: error from auxiliary database: ORA-01017: invalid username/password; logon denied
When executing SQL involving ANSI syntax OUTER JOIN's Oracle first converts this to its own native syntax before executing the SQL, and sometimes this conversion is not totally transparent thereby affecting and restricting the execution plan produced.
This started when I had a long running query, and it happened to (more...)
Previously I showed some of the issues with allowing NULL values in columns and how indexes might be ignored by the Optimizer. All of the examples I gave involved single column indexes
only, and showed that NULL values are not stored in such an index. As others have pointed out (more...)
It is quite clear that Oracle does not store NULL values within indexes (B-Tree indexes specifically, being the most common type used within Oracle). This has been the case for many years - I remember reading about this in the version 7 days over 15 years ago. My understanding was (more...)
On the one hand I understand the added value of the concept of a "NULL" value - meaning that no value has been stored in a column in a row in a database table. On the other hand I have always felt that allowing NULL values in a column leads (more...)