Block Dumps

As discussed previously, one of the nice features of an IOT Secondary Index is that it contains the mandatory Primary Key of the IOT, which is always maintained and can be used to access the necessary rows of the IOT regardless of  row movement within the IOT itself. This can also be beneficial if only the PK [...]

Man, its been ages since I had free time to update the blog, what with birthday parties to organise, Roger Water concerts to attend and Radiohead concerts in the planning !! OK, time to take an initial look at Secondary Indexes for Index Organized Tables (IOTs). If the IOT needs to be accessed via the Primary Key (PK) column(s), [...]

I’ve recently returned from a great two-week holiday, firstly at the Australian Open Tennis (what a final !!) and then up at the Gold Coast in not quite so sunny Queensland. Time now to get back to my blog In my previous IOT examples, we had a very large column called Description which we didn’t [...]

In my previous post on Index Organized Tables (IOT), I introduced the concept of the IOT Overflow Segment, where we can store columns that we may not want to include within the actual IOT index structure. Before we move on, I just wanted to cover off a few additional points that could be a trap for the [...]

In my previous introductory IOT post, I illustrated how an Index Organized Table (IOT) might be worth consideration if most or all columns in a table were to be included within an index. I’m going to use a slightly different demo this time, replacing one of the columns with a much larger DESCRIPTION column, one which [...]

Thought it was high time that I covered in a little detail the subject of Index Organized Tables (IOTs). When used appropriately, they can be an extremely useful method of storing and accessing data. Hopefully by the end of this series, you’ll have a better understanding of IOTs, their respective strengths and weaknesses and so perhaps [...]

The intent of this blog piece is just to bring together the whole discussion of block dumps and how we can use block dumps to demonstrate Oracle behaviour. First, let’s start with a fresh little demo, creating an index on a NAME column with 500 entries (note this specific demo uses an 11.2.0.1 database running [...]

Having already covered general block header details relevant to several different types of Oracle blocks (Block Dumps Part I and Part II), the next part of the block dump is relevant only to index blocks. Below is a dump of the index only section of an index leaf block dump: Leaf block dump =============== header [...]

OK, let’s look at the next portion of the index block dump.   Following the hex dump of the block (as we ended Part I of the series) is the second part of the block header (see below):    Block header dump:  0x0201490a  Object id on Block? Y  seg/obj: 0x1c205  csc: 0x00.2d11214  itc: 2  flg: -  [...]

I’ve previously looked at how to generate an Oracle block dump, time to now go into a little more detail. As I mentioned, a block dump is a formatted representation of the actual contents of an Oracle block. Producing strategic block dumps can be an extremely useful method of determining what might be going on in Oracle under the [...]